I've replaced 3 engine cases. 2 had belly bans and 1 didn't. Sorry, I only have pictures of 2 of them due to a crashed laptop. All 3 of these were 2-whl'd repairs and were paid for by their insurance company ... they hit something.
This one was puncture when he rode over a wrench made in China.
I believe this one was damaged by running over a very large bolt.
I was also involved with a 4th repair. That repair was done by another shop that needed advise. Apparently trike owner rode over raised RR tracks with a sloping road up and back down on the other side. However, apparently he was going way to fast and "flew" across the tracks. His headlamps did not see the rocks in the road on the other side. Not only did he bust out the bottom of his engine, he also did trike damage.