[JimD]

I would try an impact wrench rather than more pressure. The repeated impacts are less likely to damage the cover.

An illustration may help. Many years ago I had a dune buggy with a VW engine (air cooled horizontally opposed 4 cylinder). The flywheel attachment was one large nut and some dowel pins. I was removing the flywheel for some reason, can't remember what. I put a large pipe on a 1/2 break over bar on the nut and picked up the back of the buggy and the nut still wouldn't budge. I borrowed my uncle's worn out electric impact wrench. A few seconds banging on the nut and it was loose.

I would go for relatively low torque. I would use my 18V cordless first and then maybe go to my cheap 1/2 pneumatic. I WOULD NOT go with a big 600 ft lb pneumatic.

Jim