Regarding your 7448 and the CPU Plugins problem. I have found this Japanese retailer that from the rough Google English translation seems to say they have a custom updated/edited CPU Plugin file that fixes the 9.2.2 crash problem with 7447 upgrades:

http://www.vintagecomp.com/sell/Sonnet/Encore7447.html

Here is a direct link to the file:

http://www.vintagecomp.com/sell/Sonnet/updatedCPU.sit

I believe it will also work with 7448 upgrades as well. I don't own a 7447 or 7448 upgrade so I have never been able to test out this file to see if does what I think the translation seems to be saying.

Try it out and report back here to tell us what it does.