The moleskin idea is great, but I didn't suggest it for good reason (same as the felt). Since you have direct contact, you could face sweating issues during high humidity and the glue can bleed through to your firearm with either of those installed. Not saying they will, saying you can have the issue. I've already experienced this and I wasn't happy with myself, thankfully I had Goo Gone on-hand.

So, if you have the room for the felt pads or the moleskin they're a great option. If the tolerances are tight and the room just isn't there, then it's a judgement call.