I had a CF frame repaired --but it was just a cracked chainstay. I might be a little more wary of a downtube. But I checked out Calfee and they wanted $350 just to look at it --repairs may go up from there. I ended up getting it done for much less by a guy in Minneapolis. Excellent job too. I was considering doing it myself but it was a pretty high end bike and I decided to use someone with experience. I can dig up contact info if you're interested.