Looks up with binoculars.
Yeah you guys are WAY over my head.
I do agree solid chunk drilled out should be better. I love DIY though
Mass = better, thats what I read. and the F1 pot Kal let me borrow got rid of that nasty 40C swing Dicing wPrime... trick is MASS alone is not enough. Need to get surface area, or you "cold substance" is not removing enough heat. Too small (say fins in the bottom) would be a problem because they would get brittle and also clug up with condensate.
Rods like an old ram sink might work decent, but too hard to mill unless its a two piece...for DIYer though... its an option
especially with 3" diameter to work with
Use some thermal tape a bunch of copper ram sinks (old style 1-2" high kind) torch it to melt the tape and get to freezing
Just an idea...