When I make up rostrums, I work to 8? x 4? to suit the off  shelf size of the deck plate boards, with folding gate leg construction. Which is made up of 2 x 8? & 3 x 4? gate leg frames which are butt hinged together, so when the top is removed the rostra can be folded flat for storage . This is the same when doing 6? high gate legs, without the need to double up the timber size, as each 4? wide gate leg frame is hinged between the two  8? side gate leg frames, doubling up the actual legs. I use drop pin hinges but they can be just standard fixed pin hinges.
So I would just butt up two 8? x 4?x 6? rostrums & clamp or tie them together.

Joe, can you post here or email me a diagram of what you're describing?  I'm having trouble visualizing the set-up.  (I'm too visual a person, I need pictures. :) )

Forgive my ignorance -- despite what I've been able to do, I'm still rather new to this. :)
 
I'm familiar with gateleg tables -- I have one in my dining room -- I just can't picture how to construct gateleg bases for platforms.  It's just not clicking.  Sadly, I can't find any pictures of any online, either. :/

Great drawing Eddy!
But no not quite what I'm on about.
I have emailed you my pathetic  atempt!
One thing I forgot to put in the drawing I sent Eddy.
Is under the top board deck plate, screw & glue flat pieces of wood, to fit next to the gate leg top rails. Which will square the rostrum frame up & stop any movement. It is not necessary to hold these wood noggins onto the frame, as it is normal to tex screw the top deck plate down on to the frame.