I have been doing more research on other s/c (roots) kits for hondas, cobalts, etc. (4 cylinders) and looking at the intake designs on those and they seem to have a much smaller plenum feeding the runners. So I might try that with the new design, mimic something similar to what another company has done.
If I am able to make the plenum smaller I will be able to add better bracing on the manifold.
Something similar to this with more runners
I am not able to do vibration analysis, because I dont have that capability. Although Im pretty sure we are about to upgrade at work, which will include vibration analysis. I dont think this will be as big of a problem as the end of the plenum will be supported. You mentioned the weight hanging down, and that part will have supports running to the motor, so it wont be hanging. I would agree with you otherwise.
Thanks again for the input.