G'day Kim.
#1 Yes it is good to utalise a datchman, however I doubt you would have time or be allowed by the theatre to piant & use them, especialy with a 2 day bump in & the need to focus, set lighting, dress the set & have a 'tech' & 'Dress' rehearsals.
I assume you are making the flats, are they 'soft' or 'TV' flats?
if so ensure they are square & fitt together neatly & not like a dogs hind leg!
I preffer when jioning flats together, to lash them up with sash & cleats. Whith soft flats this especial good , because when you wish to strike them on bump out. Just unlash them & let them fall & float down to the stage.
But using the loose pin hinges is equaly as good.
However with the sash cord you can pull the flats into square, with extra purchase.
[The sash is attached to the head rail of one flat & run across to a cleat or purchase scew in the next flat & serpantined between the two flats stile rails & cleated off at the tail rail.
#2 You would only need a 'Ledger' to hold the wall flat & reduce the waving. However if you design the walls with step in or out alcoves & book the flats. This will help & support the box set better. Which also helps with bracing, especialy for the door flats & I guess the window seat would set into a bay window.
Use either the adjustable 'stage braces' or 'FRENCH braces' [which are wing hinged on & fold out].
The theatre may not allow you to put stage screws in the deck, in which case 'sandbags or scene weights are used.
But check with the venue to see if they have braces & weights avalable.
Here is some of the hardware they could have in stock & is available to help you.

I hope this helps?

Originally posted by Ken W Gaafa is the pro,

Sadly Ken too many smokes & coffees have put pay to that. It has been a long time since I have solicited myself & had my palms crossed with silver.
When I used to produce flats I would always set them up for loose pin flap hinges, useing a template to standardise the hinges [Hinge halves on a piece of timber to ensure they are all the same, after putting the skin on] Also with the pins, tieing them  to a cord & attaching it under the hinge half held by the screw, helps to ensure it was always on hand & also painting the grip of the pin white. However being long in the tooth I preffer to still use the sash & cleat as well.
The hinges are not cheap, but well worth the outlay.
However with the bracing, booked flats & placed on angles to the others, will stable the set. Also reduce the need for dutchmans being used, employing corners, nooks & cannies into your design, ]The Edwardians along with Victorians, loved their nooks to break up a straight wall.
You may need to mask behind the jionts, any strip of black tatt will do, to mask light & any movement from behind the flats [gaffer & other tapes have a white or grey sticky side].
Aviod nailing anything that would have to be denailed during Bump out, because it rarely happens & only become a wepon to inflict harm latter. Use Tek screws that can be removed with a battery drill or gun, the luvvies [warm props] love to play about with tek guns!
As I mentioned check with the venue, I'm sure they will have braces & a lot of hardware you can borrow or even half inch, with their aproval?

as it's your first time & before your deflowered!
A few other things going into a venue, especialy a pro house. Try & ensure your are as self contained as possible, regarding consumables like gaffer tape & the like. A lot of groups tend to forget about the extras that can be addded to the final bill.
Either yourself or the stage manager set up one of those generic 'Order Books', so when there is any consumales used or extention to the orignal hire contract, ensure the venue needs an authorised order number, to be able to get paid.
Also watch out falling into the trap of paying for things like a lighting design. Inevertably all you get is a standard rig wash & a few specials - which is thier normal standard rig anyway.
Further work out all you needs as dictated by the script for cues & changes before hand {[5 P's 'Pre Planning Prevents P*ss Poor Production]} Because time is money - so put a meter on it!
Get yourself a 'white board' & list all the jobs for the Bump In/Out & cross them off upon completion.
Marshal your mob to move in the venue quickly & focused on the job in hand, use a few chosen parents or ASM's to orginise them, especial the cast to stay off the stage, unless invited to do so.

Kim what type of flats are you using?
The 'Ledger' is a lenght of timber, used as a stiffener across the back of the flats.
Taking out the bay window & door flats, you would have about 12' left, made up possibly of 3 x 4' flats, set up one on each side of the element flats.
If you use 'reveals' on the bay window & a return to mask the interior door opening, this would stabilise the wall, along with french or stage braces on the flats. With the door flat, utalise a stretcher iron on the tail of the flat actoss the opening. This will stop the door flat from walking or wandering & the door from jamming out of square.
If your using soft flats, it is a good idea to step the door flat, with a small gap between the door frame & the flat on each side, this cuts out flapping when the door is closed.
With the box seat in the bay window, use a 'jogger' flat the same width of the seat & place a window flat upstage. Just make or find a woden 'coffer' box to fit  with a padded top or whatever. This would be simpler.
You can add a dutchman to a booked corner, however  even using roller bandage or most materials, there will be a fold crease mark as with any  corner, but will not be noticed only by you.

I am still playing with the dimensions of my set walls. I don't know the correct way of measuring a stage (where to start, where to end) but from my rough measure, my stage is 52' by 28'. Given those dimensions, does a 26 ft. back wall seem too large? I am planning to get into the theatre and look at through the eyes of this set. If that makes any sense.

KIm

Hi--