Our cat samantha is 17lbs right now, but has been up to 22lbs in the past. My mom usually does the nail cutting and Sam hates it. Actually, one time, when she tried to do it while having Sam on her lap, the silly cat peed on her. That didn't happen again. Instead, mom takes the clippers and essentially "squats" on the cat, kneeling on the floor with the cat between her legs. I guess putting her bum lightly on Sam's back means she can't stand up to run away. Just need to make sure that you block her with your arms in the front and put your legs together in the back so that he doesn't slide out of the hold. It seems to work well enough, and would save some $ for a vet visit.
Otherwise, good luck with the nail covers.
Otherwise, good luck with the nail covers.