the downtube was a foco tube. crazy thin... crazy shapped for steel. it was meant for road bikes and superlight xc frames. it crimped near the head tube where the internal butting goes from thin to thick.
as for the adaptors, you are correct they sit too close to the rim to run a vee... super smart- i think they just figured everyone ran xc rims for trials or something. anyways, i will be making my own that wont suck some time in the future, if they work i will be making a bunch to sell to people like me that hate magguras and see no sense in ever putting 4 bolt mounts on a frame. when i get a finished adaptor i will post about it. o yeah and they wont be stupidly overpriced.