Remove grips from K2 carbon pole

I want to shorten these poles. The grips themselves come off easily, but the sheath on the inside isn’t budging. I’ve been heat gunning it and trying pull it off but it won’t budge. Is this epoxied to the carbon and it’s hopeless or do I just need to pull harder?

All else fails I’ll just cut them a bit shorter and cut some pvc pipe in half and put it around the bottom to make up for the lost bit on the top.