Check out the update linked at the bottom of this post!
I went ahead and printed a full set of the final design from my original post as a placeholder until I could make the truck tolerancing changes that I had planned. I thought that this set would work, but wouldn't be perfect. Turns out they wouldn't work at all.
To get the test print to fit last time, I had to sand down the spot where the truck would slide into. After printing the full set, I tried to repeat this process. It was then that I realized the tolerancing problems from before were more serious than I had initially thought. I was under the impression that the tolerancing was slightly wrong but that sanding fixed the problem, but I discovered sanding was not enough to do the trick and the fit was just too small. I spent a couple hours carefully trying to sand away enough material to make them fit before I realized this but was worries about the strength of the piece after taking away material from already thin walls. In the process I was using a makeshift power sander and actually melted some of the plastic and in an attempt to press them on, almost ruined a bearing. It was about that time that I realized I wouldn't have a set of fenders just yet and would need to be patient and try again with the print.
I went back to my CAD file and sectioned off just the part of the fender that would be interacting with the truck. I printed three of these as test fit pieces with three different inner dimensions, increasing the previous inner hole diameter by 1 mm, 1.5 mm, and 2 mm. This was done using a Prusa i3 MK3S+ in PETG with a layer height of 0.2 mm and a 20% infill. Test fitting resulted in the 1 mm increase piece fitting the best. Knowing this, I updated the fender file to reflect that and printed using the same setting as before except I changes the outer shells from one to four for more strength on the fender walls.
truck tolerancing sample pieces
I ended up going with the middle size. They didn't snugly on all of the trucks because all of the trucks were slightly different sizes. Instead of trying to print a custom piece for each truck I just used electrical tape to create a press fit.
truck tolerancing sample piece with electrical tape
After deciding on the tolerancing for the trucks I reprinted the full fenders and installed them on my board. They look fantastic and fit really well. The electrical tape is helpful in creating friction between the two slick surfaces of the plastic fender and metal trucks so they feel very secure. I can't wait to take them for a spin!
printed fender (left); full set of fenders installed on my longboard (right)
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