Personally I don't think it's worth the effort to stack copper. Maybe one day that might change, I doubt it will before I die.
there was a thread about this a while ago, I'll try find it if I get some time or maybe someone knows where it is.
Copper is more of a base metal IMO and not really a precious metal. Since its so cheap, you can't really store a couple of tons of copper at home can you?
I have a couple hundred copper rounds and a few bars, but I didn't get them thinking they'd be moving in price right away. I guessed I'd put them away for a decade or two and see how they'd do as vintage shtf curios.
I've stacked quite a bit of copper - rounds and bars. Every time I buy some silver from Maggie, I augment the sale with copper to take advantage of the postage. The copper rounds make great presents when silver is too over the top. Also the same designs on copper beat silver easily.
I have 16000 pennies,have been slowly selling them off at about 25-30 cents each,i cannot see alot of upside in copper. If you really want to stack copper buy Aussie Half Pennies and Pennies,you can buy them local so the postage is somewhat cheaper