Yeah I think of the C64 as a UK machine too for some reason - I guess we got all their marketing - but it's actually as American as apple pie. Based on what I've read it's more likely that Commodore just rushed it out the door regardless of the engineer's cooling concerns, and the vent blocking RF shields would have been slapped in there in a panic to get approval. My C128DCR for example was designed to have a fan mounted in the PSU to draw air through the PC but although the mounting holes are there, the fan was dropped to save a few bucks. The CR stands for Cost Reduced. Every cent counts I guess and PCs became obsolete the moment they left the factory back in the day so why aim for longevity? That sounds like a more scientific approach - I've also heard of peeps putting a drop of superglue on the corners of the heatsink but that sounds like a potentially messy cleanup job when you want to take it off again. My paperclips could of course fall off and short something but I'm confident that won't happen.