I aligned the hinge brackets within 0.1 degree and started riveting the nose and bottom skins to the spar. I kept checking the alignment after each rivet and it never strayed from 0.1 degree.
The rivets on either side of the hinge bracket are too close to set with my mushroom head and the plans mention I need a long shank head for this area. Unfortunately, I don't have a long shank head. The plans do mention that you can substitute the MK-319 blind rivets in a couple of locations, but those locations are on the inboard side of the hinge brackets and not on either side.
I'll have to reach out to Vans for some guidance. I was hoping to finish the left flap this weekend, but that's not going to happen I suppose.
Update 10/1/22: I reread the plans and realized the two substitute blind rivets are on either side of the hinge brackets. I riveted them this morning.
I made some spacers to hold open the trailing edge for access to rivets
