Very nice quilt!
I agree with Tartan---Like you, I once had to finish a quilt for a non-quilter who started it when she was laid up with a full leg cast. Only it was worse; she had already hand sewn, with half inch stitches, the T-shirt squares together, without any stabilizer! She wanted me to quilt it! Yikes. I ended up adhering stabilizer squares individually cut to size onto the back of each "square" (they didn't necessarily have ninety degree angles) before longarmming it. I made the stabilizer fit in between the seams. It wasn't easy. After quilting, I ended up with a few tiny tucks in the back, a much better result than I feared. She was very happy, but I'll never take that on again.