Gearz,
I've finished the builds of the bridge B2 and the LB B2 and alternate. The bridge module worked well. I posted comments on that already. I had some trouble with the very front - some buckling and edges not quite lining up. I think most or all of the issues could be solved by moving the tabs off the very front panel so that everything gets glued in place, then the front panel folds down to hide it all.
Here's what I mean.
As for the LB modules I prefer your B2 version over the alternate. Keep the main section of the LB the way it is in your B2 and add recesses in the end caps which then glue on as a unit. Is that clear?
Here's a bunch more reference pics of the paper and plastic kits.
Plastic kit on cutting board for ref
Paper and Plastic Bridge modules - top view
Paper and Plastic Bridge modules - front view
Plastic kit - side view
Plastic kit - elevated side view
Plastic kit - bridge module
Plastic kit - engine module - side
Plastic kit - engine module rear
Paper and Plastic LB modules - top
Paper and Plastic LB modules - front
The plastic kit dimensions are roughly
17" long by 7" wide by 2-1/2" tall (length is nose to tail, width outer LB edge to outer LB edge, height bottom of LB to top of engine module. See reference pics above for a side view of the plastic kit)
LB measures 8-3/4" by 1-5/8" by 3/4" tall
Bridge module is 5" long by 4-1/2" wide by 1-3/4" at the rear and about 1/2" tall at the front.
The section immediately behind the Bridge module is 2-1/4" long.
The central section (where LB arms attach) is 5" long by 2-1/4" wide by 1" tall. The bumps on the bottom add another 3/4". I'll take another reference pic of that next time - didn't think of it this time.
Engine module is 4" by 4" by 1-3/4" tall not including the bumps on top and bottom.
If you want any other ref pics or dimensions let me know.