I know where you're coming from..............quilting on someone else's quilt scares the heck out of me. What if I ruined it, put a hole in it, they didn't care for how I quilted it,etc. I've had my system since 2012 and I've quilted only a few quilts for others. I was so nervous that I'd do something stupid on it but I got thru it but don't care to go thru it again. You've gotten a lot of rave reviews on your quilting so maybe you should try a few and see how it goes. Be sure to ask them how they want it quilted, time line, who provides the backing, batting and thread, binding services and I'd ask for at least half the price down payment. You might make up a form for them to sign stating who, what and where about the quilt so there's no confusion at the end. I've read a couple horror stories here online that tells me I don't want to get into it but I'm also over 70 and I don't seem to quilt as often as I used to.
Good luck!!