Any particular reason u put the throttle body on the side rather than the front? Cable length? What is it about the passenger side that attracts u to it? I noticed that the previous tubular style manifold u were building also went to the passenger side.
I like the wavy shapes of the intake floor. Was it made from piping or sheet metal brake bender? From a design standpoint I'm not fond of the removable access panel. 1) Bolts on thinwalled sheet metal cause warpage in between bolts. 2) The threads protruding into the plenum could potentially hurt flow. 3) The inconsistent thermal expansion of the top of the intake (i.e. the access panel and the plate it bolts to) lead to possible leaks.
Things I'd (I'll?) change/ add for future designs:
1) Thicker material (as per your recommendations)
2) Relocate Throttle Body to front.
3) Rounded sides. Maybe 4" or 6" round tubing cut in half, welded to sides.
4) Entire plenum roof would be access panel. Possibly change access panel to front of plenum depending if plenum size allows a man's hand holding appropriate wrench to fit.
5) Taper towards rear of engine w/ new throttle body positioning. (I noticed yours tapered towards the front w/ the rear mounted throttle body).
6) Possible mechanical linkage to avoid going to a new cable.
7) Possible trumpets w/ flat floor. (sdsefi.com had an article showing how to make your own trumpets but they seem to have removed it).
Kurt
Argh... guess I'll stick w/ the plan...