When you are paying for a light weight silencer and hold it in your hand it suddenly it isn’t as light weight with and additional 100g.
That’s the first time I have heard about heat retention on F&D, they must retain the gasses very well. If they melt a protector, I would say it’s a not very well made item. They should be heat resistant.
I use an inconnel Oceania Defence quick lock, it gets very very hot. Simply I don’t touch it. Being inconnel it is designed to handle full auto so there is no integrity issue with heat cycles. Any silencer that captures hot gasses will get hot, occupational hazard, I guess.