Recently converted an old Miyata and I'm liking it so far, I just want to paint the frame. It has these two plastic "vents" on the top tube and they look like they are actually built in to the frame and not just stuck on. Can anyone confirm this or not? I don't want to crack them off if they are structurally part of the frame. There are also these two square nut/lug things on each side of the down tube. Any idea what they are for?