Yep, the "garmin" mount could be better in terms of adjustability and I went with mine all the way to the top of that top spacer. If I needed to slide it more backward I would cut the part of it since it's cheap carbon copy. And I'm pretty shure that my handlebars came with silver mounting bolts for the garmin mount (but I'll check and report). And I thing my mount comes with two slits for the bolts, not one long cutout.
Yeah, I had to use the silver bolts since the black bolts that came pre-installed were too short when you used the plastic spacers.
Congrats on a new frame! I'm looking forward to see how your bike goes when built.
Yeah, thanks. However, I'm not going to fully build the bike all that soon. I have to pick up my PM crank (Magene P505) from my parents' place the next time I visit them since they wouldn't ship to where I live (I bought it from the official Magene website, not Aliexpress). I just put the frame together to check if everything is okay.