I know it's not traditional, but I'm sure those old timers made their stocks fit their barrels very closely. The breech end of my barrel has over a 1 16th inch gap between the bottom flat of the octagon barrel and the stock. I wonder if those gaps between the barrel and the stock affect accuracy or could eventually crack the stock?
As with anything, it's your choice. I had two "nail driving" unmentionables that were glass bedded. The powder was measured out to a gnat's [behind], the brass was trimmed to an exact length, each time, each case. Plus a lot of other "monkey motion" but both S.O.B.'s could literally drive nails.
We shoot black powder. If you immaculately clean the bore after every shot, if you can measure the black powder to litterally the grain every time, if the projectile is identical with every shot and the patch is the same, if you can get the flint or percusion to ignite the charge in the same way every time, and you have the time and money, go for it. Glass bedding can help as long as all other variables are covered. I found it useful with an unmentionable, having an inch and an eighth stainless steel target barrel was very helpful too. Really, if it's something you want to do, go for it. I'd like to know if it really helps, just for the information. Personally, I shoot black powder because I am addicted to loud noises, smoke, and knocking spider webs out of the rafters at our covered shooting stations. And getting smaller groups is always a challenge but for me, not a requirement any more. Hey, good luck regardless of what you decide to do.