I think the birch is a more period wood. I do a lot of historical reenactment-type stuff. The poplar was also fine, the woods are very similar.
I ordered the poplar dowels on Amazon: https://amazon.com/gp/product/B00C4TPZKK
I tried with wood dowels from HD, but the size is not regular enough. I found that on amazon; it's perfect (https://www.amazon.com/gp/product/B08XQQ69WD)
I use a paint tap to keep them plat ( I cut them 20 per 20 ). Easy to do.
a) buy a pack of wood shims at your local hardware store (example)
b) shove them under wheel to desired angle
c) buy longer M6 mounting bolts (measure carefully so you do not go too far into the base, the max the bolt can go into the base is 12mm per this drilling template) and some washers because the bolts will be at a bit of an angle
maybe there's a better "tightening an angled bolt in to hold it in place without warping the contact surface" solution that I'm not aware of besides a washer or two
I bought these knife scales from amazon. I tested a corner with a couple of coats of tru oil gunstock finish. Looks great. Going to use it for the next knife and I ordered another set to make a sheath out of. Going to a leather store tomorrow to pick up some tanned hide, some dye and wax, a few tools.
Hopefully in a couple of weeks I'll have something that will look really nice.
I appreciate your input as well as how I have 100% upvoats and no downvoats, they tell me I'm for sure on the right track!