i built a box for my buddy whose subs didn't come with a cut out, so i traced around the sub, then scooted in like 3/4", drew that out, then cut....might try kicker's website, i think they you can print it off there.....
ur pretty much screwed bro. i had a friend where i built him an enclosure for a 12" L5, and dayum that cutout template helped alot. i would suggest finding someone that has a 15" L5, that can lend their cutout for u.