Anyone repaired a cracked AC shroud?

Call around to the local RV stores. When mine cracked a year ago I found a used on that was in great shape for $40.

If you go the epoxy way I would take a small drill bit and drill a small hole at the end of the crack and this will help to stop it from traveling more. You could epoxy a light piece of plastic on the inside along the crack to give it some extra support.

I've been using West Marine Six10 Thickened Epoxy Adhesive for all types of fiberglass crack repairs with excellent results. This stuff can be put onto a vertical seam and not flow downhill. Clean with Acetone or similar and maybe roughen with sand paper, etc.

It's a two-part epoxy that comes out of the nozzle already mixed due to their unique nozzle, but you can also just squirt it out without the nozzle and mix on a flat surface if desired. You may be able to find a two-part epoxy of the thick type in a big box store, too. I think that would work for you, too.

When I cracked mine I taped it form the inside with some eternabond tape I had left over from a roof job. Worked well.

I never had any luck with tape holding up for any amount of time.
I have had good luck with fiberglass cloth and resin. I rough up the surface with 80 grit sandpaper before fiberglassing.

Never used it to repair an A/C shroud...but Gorilla Tape is serious stuff. It is stronger and stickier by far than duct tape.

Aside.. completely replacing a standard RV A/C shroud is an easy fix and not all that expensive.
Good luck with it.