Heaterbox Pipe Passthrough - Reinforce vs Remold

It's freaking cold outside!

OH CRAP, I just noticed you are in CO. :D
Myself I would put duct tape on the back side of it and paste that area over with something like JB quick.
Sets up in 15 min, drillable and won't crack like epoxies.
After the front set you could pull the tape and do that side if you want.

I read all the responses and also have quit a bit of hands on with this kind of stuff already.
This box had the front ripped out where the J hook bracket was. (right above the door)

heater ready.jpg