Max number of shirts in a T shirt quilt

[Doloris]

I've made dozens of t-shirt quilts. The number of shirts you will use will depend on the size of the the t-shirt block - which is determined by the size of the largest logo on the shirts you will use. I've written a t-shirt quilt tutorial if you're interested....

T-Shirt Quilt Tutorial for beginners | Seams to be you and me

I think this is a great tute and pretty much how I do my tee shirt quilts. I do my horizontal sashing all in one piece though. Personal choice. Does take a little more effort to get the rows lined up, but no seams in that sashing.
Just look for a very light weight non woven interfacing and all should be good.
I've had to piece in the corners of a tee a few times too, and you never see it once the quilt it put together