Perhaps he could clarify but whatever shape air is going to be his enemy.I think the op meant big squares rather than wrapped rounds.
Same as above, I know a couple of people who tried it but never more than once.
I wouldn't have thought it would be any cheaper than wagon silage but with more complications and risk.
We use mash on clamp. It is great but i wouldn't try it on bales.About 20 years ago I saw someone put the bales in a roofed clamp and then covered the bales in mashed potato and used no plastic sheet. He swore by it. It looked a horrible mouldy mess to me.