Anyway, I decided to make use of the messed up tubes by building a frame out of them. I did not have enough 20mm tubes, so I made the seatstay out of bamboo - also as a reference to where I'm coming from (building Bamboo bicycles). Again I used prepregs for forming the connections of the tubes. This was quite straightforward - cutting pieces of 5x5 cm or so and putting them (cleverly orientated, of course) on the tube proved to be easier with prepregs than with a wet fabric as I normally do for Bamboo bikes. I vacuumed the whole frame in the oven. The whole lug-making process was simple and the result was nice, given that I did not spend more than 2 hours on it. One one position I put too much breather fabric in the bag which removed the local pressure from a concave part of the seatstay attachement, so the uppermost layer of prepreg delaminated there when I ripped off the nylon. But that could have been easily solved with a bit more care when making the vacuum bag.