It's not perfect from stopping him trying to reach his hands in there but at least he isn't able to do a belly flop into the tootsie rolls anymore.
Use a sharp pair of scissors to cut the hole. The grill is just flexible plastic. Then use an exacto knife to clean up the rough "edges".
Get it to fit in your space as best you can. I just scrunched up the gate and then cut some old used green foam board to fit it into place.