There's no reason why you can't build a damn nice sled on your own. From experience I'll tell you that sometimes it's cheaper just to go buy one, so if you're doing it to save money the I'd really step back and take a good look at what my total cost would be ( what is your time worth?) But, if your doing it because you enjoy fabricating and you'd like to be able to say to peopl " Pretty cool sled huh. Yeah, I built it myself." then go for it. How are you welding the hull? Are you going to T.I.G. weld it, or are you just going to use a spool gun?