I've had the opposite problem with my friction hitches on the 10.2mm. I started out running a 6mm very stiff prusik cord tied as a distel hitch and it got hung up far too often. I now run a few 7mm accessory cord distel hitches and an 8mm prucel prusik for my foot loop to ascend, all with more flexible cord and it's worked much better.
Last weekend I was practicing ascending and rappelling in my garage and one of the distel hitches got hung up so badly I had to practice a self rescue. I run an ATC or figure 8 for rappelling with a distel hitch backup in 7mm cord and I've found the backup hitch has to be below the rappelling device or it locks up too hard to be functional. I do however run a prusik knot on my lineman's belt with a paracord/ring tender and that works flawlessly with very soft 8mm, but it never gets my full weight.
If you get the rope and have issues with the distel hitch not grabbing, and it's not because your cord is crazy stiff, I'd try dressing it more neatly first and if that doesn't help I'd add an additional wrap. If you still have issues with it not grabbing, you could always go to a thinner cord, like 6mm, or even a prusik hitch, but I think it would more likely be user error at that point. A michoican hitch with the 6mm also worked well and didn't lock up, but was more finicky and did slip if not dressed perfectly, but I think that was more because of the stiffness of the 6mm cord. I'm currently using 3 different types, two 7mm and one 8mm, with 2 being medium stiffness and one pretty soft. They all work very well.