I use the Red Snappers, love them, and don't have a problem attaching them, but my hands are pretty strong. I do think my Snappers have loosened up over time. My leaders came with my machine, and I think they are cotton duck, pretty substantial fabric. I attach the top of the backing first, by extending the leader all the way to the table (which apparently you can't do because your leader is too short) and then I get "inside" the frame and snap the Snappers on. Renae's video show her just bending over the frame, which I have done occasionally, but I'm a bit rounder than Renae and I find it easier to get inside.
I attach the bottom of the backing by rolling the leader so that the Snapper is on the top of the pole, and I can press against the pole with the top of my hand. I float the top, so don't use the Snappers for that. It is a lot easier to load the Snappers if you start at one end and work your way along, rather than trying to press down in the middle. Gemrm's advice to stretch your Snappers is worth a try.