As long as you use lightweight non-woven interfacing, that is.
I considered skipping that step (because I love skipping steps, especially those that cost $$), but it was totally worth it. No stretching or curling or any of the other annoying things jersey knit does.
I went with the cornerstones and I think it looks great! Plus I only needed a yard of the gray instead of 1.75 yards.
Tycho "helps" line up the seams.
I wish I could count the t-shirts in my stash busting - three 14.5" squares in each WOF busts over 2 yards. But I think that would be cheating.