So... I'm buying the metal Etha bolt ('AM'). I suspect it may result in some breakage, but it means long term, I won't need to worry about the rubber tips coming off. Normally, I wouldn't bother with such a thing... but as I have filled in the old hopper hole with JB-Weld, that causes a tiny bit of surface difference and I suspect causes the tips to come off sometimes. Although I totally admit... this only happened on less than perfect rubber tips (i.e. old).
This does however, open the possibility that I may.... 'MAY'.... cut my breach for FSR. This would mean some substantial rework if I did this, and may mean I swap to making a breach adaptor of sorts instead of merely using JB weld. Will see how the gun runs with paint for now.