In every "Universal" ROM (IIsi and up?), there is a table that contains information about specific machines the ROM knows about. This includes things like what address decoder it has, VIA initialization values, slot information, RAM bank sizing, onboard video setup, how to access PRAM, RTC, etc. I'm still noodling through what does and doesn't refer to this (MMU setup has its own tables for instance), so some of the information in the table is authoritative for some things, but not others. As a result, I can't say whether something should or shouldn't work with any certainty, but...

The Quadra 650's RAM setup information in this table indicates address space and probing for 64MB/socket.

All that really matters is the empirical test, so yeah, it would be interesting to see.