Hello people!
I'm building a Big Dummy for an upcoming cycling tour. However, I ordered a pair of P racks from Xtracycle and I'm clueless on how to install them. On the image below you can see my problem.



As far as I understand the rack should simply slide into the tubes 4 on the rear. However, for the longer tubes near the middle of the bike there is stuff blocking on the inside so the racks can not completely slide to the bottom. Whats blocking is a threaded hole on each side of these tubes (see the image red arrow, you can screw a bolt all the way through on this location) which is sticking out on the inside of the tube like 5mm for each hole.
So when you slide in the Xtracycle P or V rack it rests on these things sticking out (it does not drop lower than the red arrow), while surely it should slide all the way to the bottom?
Anyone know whats up with that?