It sure has to be cut exactly to the slot. On the short side is even better. Half a millimetre. Then you can actually stretch it somewhat with finger pressure as the glue dries. I also like to put the glue on the vertical edge as well. All the best.
Agreed but careful when an undercloth is used, then the cloth is exactly the lenght of the hole, in my opinion.
possibly traces of soft pva glue (for tissue or books) can be used to be sure the undercloth will not move later.
originally it is often not really glued, but traces of glue from the cloth allow the undercloth to be secure.
A gooc whippen heel make wonder for the touch.
The cloth will adopt the shape of the capstan anyway we cannot believe there will be a retained profile, but if the cloth is too soft and not tense a mushy touch will happen.
Too soft can be corrected with hammer impregnation solution, or the recipe of the hat makers, arabian gum and alcohool