Sounds like the arm ripped a chunk out of the tunnel or belly pan. I'd patch it with a thick plate, rivet it in place, re-drill the hole, and re-mount.
2004 Polaris Trail RMK 136
1997 Ski Doo Summit 500
2000 Arctic Cat ZL550 ESR (in NY)
2000 Arctic Cat 440 Panther (sold)
1980 Arctic Cat Jag 3000 F/C (in NY)
"If it ain't broke, take it apart and find out why!"