As you know Mastro Livi makes a killer loom strop but it is pasted with chrom ox on the canvas side. My guess is you could ask Lynn or Don to order one with the canvas left unpasted. I have one of the Mastro's loom strops but have always used it pulled up snug. I'll have to try it with slack.

A couple of years ago, IIRC, Bart described honing and stropping routines of older razor users in Europe who stropped with slack in their hanging strop. There was also a video that someone posted around the same time with a pro barber using a strop with a surprising amount of slack in it.