IIRC, the 8 MB SIMMs definitely work in the IIsi. I bet they work in the IICI as well. I remember reading a Mac User or Mac World or both article(s) back when the LC, IIsi and something compact came out together and a big deal was made of the IIsi using 2 MB and 8 MB SIMMs.

Or that is all a big hallucination, but that's the memory I have.