Hi and welcome to PT!

My oldest cat Ripley had his teeth cleaned last year when he was almost 11 years old and he weighed about 18-19 pounds. He did just fine. His only problem was that his pre-screen blood test showed his kidney function was not at the normal level but the vet decided he needed the dental too much to not do it. He's a big cat but he was still about 3 pounds over weight at the time and he had no ill effects. Actually, my vet didn't even discuss his weight as being a specific concern he just warned me of the dangers in general.

Hope this helps a little and best of luck to Pepper. Please let us know how things go. I'll be sending good vibes your way!