IIc Plus RAM

bcl

New Tinkerer
I would like to find or build a 1 MB RAM card for my IIc Plus. The connector is the same, but apparently the cards made IIc (at least the later revision(s) that even have the connector) are not compatible with IIc Plus. Does anyone know anything about these cards? Does anyone know what exactly the compatibility issue is? Could it just be that the chips on modules made for IIc have higher latency that can't keep up with the 4 MHz CPU in the Plus?

(Yes, I know most 8-bit software has no use for more RAM. I'd still like to upgrade it, if possible.)