[GTALUG] tips on packing computers?

Hi folks, One thing about the lockdown ending is that I must hunt a new place..which means proper packing of my computers and monitors. So two questions since I must order on line. First, what is the best sized box for a tower so that there is not too much room? second, I have one older imac that is rather heavy..but important. If this should not be boxed given the weight, how should it be packed, or padded? what about those monitor slip covers, I have flat screen ones now. Thanks for any ideas, Karen