I looked at the welting and the old posts and decided to go another route.
I had a look at panel bond/car bond, 3M, Wurts, Soudals, there are plenty out there. Panel bond worked like a charm for me. No bad fits, make as smooth and nice as you want it
Since my car is a deep grey, I went with black. All the flairs were redone in fibreglass, so I'm not sure how this will hold on the old stuff, but I'm pretty sure it will work. Car bond/panel bond sticks to most materials.