quilting question

[missh.livejournal.com]

I want to make my sister a quilt for a grad present (next year, of course). my plan is to make it out of t-shirts - but not the kind of quilt with huge squares designed to show off the t-shirt designs; I mostly just want to use the fabric. my basic plan is to make a bunch of 4"x4" squares into a large grid.

here is my question. is fusible interfacing absolutely necessary? like I said, I'm not going to be making really big squares, nor will there be any sashing. basically, I just want to make one large square out of a bunch of smaller squares - no fancy pattern. I know jersey stretches, but I figured maybe if I pulled it taut as I (machine) sewed it, that should work...

the overall plan should go as follows:

1) make large square of small squares, add border
2) sew it to a backing with some batting in the middle
3) "quilt" it - i.e. sew lines/designs (I have this in my head, I just can't describe it) onto said fabric/batting sandwich

will the interfacing be crucial? thoughts? are there any major steps I'm leaving out?

thanks!

Hillary