Nice job with your first dry ice bench and very clean setup. My insulation is never that clean, wish I could get good foam like yours.

I got a few tips though. First try crushing up the dry ice into snow, then fill a bit with dry ice before adding the acetone and then fill some more. This'll create a sort of dry ice slushy which works better in my experience. You'll have to constantly mix the dry ice and the acetone to keep gas bubbles from forming on the base, but it'll let you keep absolutly constant temps for hours of hard benching, temps won't even raise during 32m runs. Even at high clocks, with that technique and my mousepot my temps don't even raise a whole degree from the start of a 32m run to end. Now if you get lazy in the middle of the run temps will rise, but if you tamp it down you've got nothing to worry about. Next, you probably don't need the vaseline, I never use it and it's never been a problem for me, and it's probably not a good idea to use a metal hold down.