Correction: oops! I misread & thought you were making a queen-sized quilt. Twin should be fine. I've made lap quilts that were close to twin-size with flannel and W&N and now with the extra nice Warm & Plush and quilted them with 1" quilting; it was still light enough for my 2 year old niece to drag around the house. Assuming the T-shirts are regular weight & you pick something lightweight to stabilize them, it shouldn't be too bad.