Let me try and explain it this way for you T-rail guys

A 2x6 bolted flat is going to be much stronger than a 2x4 mounted upright. It's all about the amount of wood behind the cushion which is what makes all the difference. When you think about it, both styles of rails are contacting almost the same amount of slate when bolted down, yet the sound effects are greater on a T-railed table when compared to a flat-down bolt designed rail. And, it also has a lot to do with just exactly how the flat-down rails are bolted as well, we're not talking Sears best here

Thicker slates were also required for T-rails, which also translated to heavier slates, which translated to much heavier frames, all of which didn't mean better playing tables. And just for everyone's info, the playing surface on a T-railed table is dictated by the nose of the cushion to the finish of the rail, not just the slate
Glen