When working on heavy projects, I will use circ's and like the previous post, put pillows behind my back. The other thing that I will do is use a stool - nursing stools, typist stools, or any small foot stool will do. I tilt mine towards me on two legs. It raises your legs a bit and then the work, when it gets long enough, can rest on your legs. By having your legs raised a bit, your work is closer to you and it helps with arm strain. I also find that I will work on heavy projects in short bursts... set a goal of a few rows a day. A few rows a day adds up over time and my arms thank me for it.