If t-rail bolts where the best way to mount the rails to a slate, the industry would never have changed. But, because of making the rails out of solid wood, the rails had a tendency to warp. And with only being able to bolt the rails flat to the side of the slates, you lost the ability to maintain a consistent cushion height from the playing surface. Then, most all of them rails were matched to the slate bolt holes, with little or no tolerances, the rails couldn't be exchanged very easy, as they had to be custom made to match the nut inserts mounted in the slates. Then, as if that wasn't bad enough, the distance between where you placed the staples holding the cloth to the rail blind was so short, you had very little room to work with installing the cloth. And, if one of the slate nuts ever got cross-threaded, it was a nightmare to repair or replace. Further more, the t-rail bold system did very little to dampen the sound effects of the balls banking into the rails, unlike say compared to a GC or a Diamond, or even a Gabriels. So, to sum up what I'm saying, in my opinion, the t-rail system of mounting rails was good in their time, but way inferior compared to how most rails are mounted on tables today.
Glen