The Plus bezel will not fit flush on the SE/30 case, mainly at the bottom indented base "pedestal" where the Plus angles backward and the SE is straight in line with the "pleated" skirt. This prevents the upper case from fitting flush.

I have never tried to secure the SE chassis to the Plus Bezel, but the parts otherwise fit entirely inside the Plus. The ports are a problem however. The entire port panel would have to cut out. But as far as I recall, I believe the SE/30 logic board will slide into the Plus chassis no problem.