some good advice here. You can do a 5 gallon batch in a 7.5 but like they said pay close attention or youll boil over. I will also add this. Many people myslef included want to go all grain, they do what you are doing and buy a turkey fryer no mill etc etc..If you think you are serious about doing this long term though I would HIGHLY reccomened you spend some money (wallet and wife approved) and get some decent equipment. I have a tureky fryer a darkstar burner and now I have an edelmetal banjo style burner. I started with the 7.5 gallon aluminum pot then bought a 10 gallon bayou now have a blichman. I also grind my own grain with a barley crusher which I buy in bulk. What I am saying is that if you think you are serious youll end up buying better equipment anyway. Can you do all grain with a corona mill and a turkey fryer, yep you sure can, and it can be good beer but with better equipment comes better process, control, and efficiency and generally speaking better beer.