I do a lot of t-shirt quilts. I don't normally sew over the logos - they can be a PIA if they're really "rubbery" and I like the look when you quilt around the logo and it puffs out after washing. I posted several pics blocksof t-shirts I've quilted recently here:
http://www.quiltingboard.com/main-f1...t-t224144.html I did one long ago with x's and didn't like the way they looked afterwards. Kind of saggy. Good luck!