Arctic cat hoods are TPO plastic, like most car fascia's, and can be welded, but it doesn't look that good when I've seen it done...
https://www.youtube.com/watch?v=4cw2AHXKmLQ
Those patches look cool, and easy!
I use Hardman Urethane epoxy in "double bubble" packets. Scratch up the back side a bunch with a sharp knife, then just glue it all together with lots of epoxy. That's worked for cracks at 90°-ish features, where the crack wanted to stay closed fairly well and the hood could be positioned to puddle the epoxy in the cracked area for strength.
If I was doing a crack in a flat area, I might use some .040" aluminum sheet as a backer, and drill some ~1/8" holes in the aluminum to let some epoxy ooze through for a little extra bite. I guess doing the same with a aluminum shaped to fit a not flat area would make the repair even stronger, but I've not had a fix come apart on it's own yet...