My thoughts as well. I have read of shims splitting and falling out when installed "the right way". I would think that by cutting at a 45 degree angle, and installing with the split facing downward and the amount of force between the barrel flare and front band you would be safe. It almost seems that the 45 degree split would absorb some of the force during recoil and prevent further shim damage. Maybe not, just thinking out loud. I have a set of castlenut pliers on order as I write this so if my split shim does fall out I will install the replacement as a whole.I see a lot of generic advice in this thread about doing things right the first time. Generally, that is good advice in all aspects of life.
What I don't see is institutional knowledge regarding installing shims by snipping them and WHY it is wrong?