Just to echo what everyone else has said, the SE/30 will definitely accept 16Mb SIMMs. I know as I managed to get some (here in the UK) and added them to my machine to ramp it up to a very healthy 80Mb. Takes a while to boot but worth it. One thing to note though is that the SE/30 has two banks of RAM (A and B) and you should fit the higher capacity modules into bank A

If you do get stuck, let me know and I'll have a look through my big bag of RAM and see if I've got any 4Mb modules lying around (got loads of 1Mb modules)