Hey Neon,
I downloaded the web page showing the Viper card and looked at the jpeg with an imaging program. The processor in the picture is the XC68040RC25M. Historically. the 040's always ran hot and need extra heatsinking. A fan with a heatsink would be better. On an unmodified A1200, that would require leaving off the CPU door on the A1200 case - not a really good idea. The 060's didn't have the heating problem like the 040's because they ran at a lower voltage (3.3V). But because of the advertised speed (50MHz), if they are using a 50MHz 060 and not one of the faster ones (I believe Motorola makes a 75MHz version), then heating would still be a problem.
Just for the record, I've got a 68030 accelerator that runs at 50MHz, which is it's rated speed and I feel it runs too hot. Probably very soon, I'm going to add a fan-cooled heatsink to it, somehow physically tied down the board to the motherboard, and leave off the CPU door entirely. This will mean elevating the whole A1200 off of the top of my computer desk permanently, but I already have it elevated anyway temporarily. Myself, I'm patiently waiting for a ColdFire accelerator board to come out. :-D