[MrForbes]

2. Depends on the loading, eh?

I'd start with big holes, because they actually reduce weight. But they don't reduce it by much. If you drill a dozen 3" diameter holes in 1/8" thick material, you'll get rid of a pound of aluminum. You'll need 26 2" diameter holes to get that same pound. The smaller the holes, the worse it gets.

I'd be seriously looking at other things to change, and drill holes in the frame as a last resort. But that's because I'm naturally lazy.