All parts of the back are not equal. I almost fell asleep while my artist was working on my upper back. When he hit the love handles though, that smarts!
I haven’t got any back pieces done but I have my shoulder. Why not try wearing a bikini top? Then that way there’s only two strings to contend with and they can be untied when he gets to the center. Your front would still be covered (you’d be lying on your stomach most likely, or maybe sitting in a chair leaning on the back?). Your sleeve is amazing, I love it.
Welcome! Your sleeve looks sick!
For your back piece, maybe wear a halter top or tank top so you can easily pull down the side that's being worked on? Only an idea. I have no experience because A) I don't have a large back piece (yet) and B) I'm a dude.
Yes, the back is rough, but you power through it because you're tough and powerful. also, don't be afraid of breaks and communicating with your artist. I get completely naked, but I'm a dude so it's different.
There's a thread here called "full back piece experience." Check it out for further ideas.