I have been following with great interest

...I like your building techniques and am going to do similar construction when I start on my build...I have a ideal for another lightweight, high strength perlam if your interested

...my design is similar to the I-joists they use to construct floor joists on a two story building.
It's a fact that laminated wood is far stronger then a piece of stock by itself of the same dimention

...my ideal is to use 3/8" ply cut at your desired width, maybe 3/4" or 1"...then cut 1/4" ply at 5/8" width...then walk over to your router table and notch a 1/4" groove right down the center of the 3/8" ply...once both of the 3/8" pieces are notched 1/3 of the way through, you will need a straight line jig for the next step to keep your joist straight and true...use your tightbond III and set the 1/4" ply in the groove making sure the 3/8" ply is flat on your table and clamp until dry...I wish I can do a drawing to show you
This build technique will yeild a very strong yet light perlam to go with your build, and if one wishes to use them as wall joists, well that will work too...I wish you luck on your build and look forward to many more pics.
Mini 4-2