I've just completed a successful upgrade of a an SI to 27.5 mhz. I'm waiting
on delivery of a 62 mhz clock for a final speed trial. Definitely needed the
heatsink. The CPU was quite hot to the touch at higher speeds until I glued
on a 90 cent Radio Shack sink. 

I made a call for reports of failures last week. No reports have arrived
here. Locally, in Seattle there is a reported CPU damage due to the user
slipping with the iron and putting a gash into the board -- not exactly
a problem due to the CPU running too fast.

I think it would be nice to have a poll to report top speeds and system
configurations including PDS and Nubus cards which were used. I'd be happy
to coordinate and report results