I have a T-rail table and have mused about making billiard rails for it. OTOH I have got bogged down working on the house/room to put it in and made very little progress on the restoration even to pocket, so don't have much ground to stand on, other than to say i have looked into the possibility.
Friend of mine in Ithaca has a 5 x 10 convertible with 1-1/2" slate in his basement. I have seen the table when installing an unrelated project for him, but have not studied it. Saving that for when i can get back to mine. Edited: PS, IIRC Geoff installed & covered friend's table. (bradsh98) Maybe he remembers and will chime in. Photos below are of eBay table.
Here is some actual substantive clues.
Apparently the convertibles bolt up through the slate (like much later GC's!) possibly with some sort of quick connect bolt or T-head bolt into a special nut-plate. Maybe the advertiser would send you some photos?
good luck, will be interested to see what you find.
smt