DD is getting a sheet set and quilt (plus a toddler bed) all made by yours truly this Xmas!
The quilt/comforter is 50 X 39 inches (my mattress is 28 X 60, a standard crib mattress is 28 X 52)... I measured from a standard "throw" and it looked nice on the bed, covers the sides and bottom, and leaves the pillow exposed (and I don't feel like it's an entrapment hazard, ya know?).
And yep, as long as the weight of the fabric is similar, you should be fine. Denim quilts get heavy, though- I made one out of blue jeans, and it weighs about 15 pounds for a twin size!
---feeling like an emu on acid---