Copper thickness and worm quesiton

[FCShiner83]

I'm doing some homework of wether I want to make my own still or buy one so I need some input of copper sheet thickness. I plan to use a turkey cooker for my heat which is propane so is 0.02 too thin? If so how bout 0.025? I just dont wanna melt nothin. Also what determines the diameter of the copper tubing you use for the cooling worm? I want to do this the old school way that my uncle did and the many men before him has done. Only gonna run corn likker off my still so I don't plan on using anything fancy.