Yes, this is grade 8 price locally, (your mileage may vary).
The studs you get at auto parts are not threaded all the way to the head, the ones I looked at have longitudinal splines near the heads. I guess you "beat" these into the car hub (so they won't twist.) The Kubo hubs are threaded all the way through, so this type of stud won't work, but regular bolts work beautifully. I tightened them as hard as I could, so far, they're holding fine. (I check the bolts when I check the lug nuts and wheel bolts.)
I only used two studs per hub because two seemed to be the optimal number. This procedure works well for me: raise the rear end with your BH stabilizers, then lean the wheel in and work it around until one stud lines up. (If your brake isn't engaged, you can turn the hub by hand.) When the first stud lines up, push the wheel onto it slightly. (The first stud "hangs" the wheel.) Raise (or lower) the rear end slightly until the second stud lines up. Once you have the second stud in line, push the wheel onto it more, raise the rear end a bit and push the wheel completely on. The three remaining bolt holes are automatically lined up and easy to bolt on. Much easier than trying to start two bolts through the wheel into the hub plate.
I figure if you use 5 studs, you'll have to be more precise in how you initially line up the wheel, not easy for me to do with my old tired back. To me, it's easier to finese the wheel using the stabilizers to raise/lower the rear end as needed to line up 2 studs. Maybe if you have better results with 5, I'll add them to mine. Let me know if you do.
BTW, the 1 1/2" bolts are just long enough to engage the whole lug nut with about 1/16" to spare. Lowe's had 2" ones, but they aren't threaded all the way to the head, so the extra 1/2" does no good. If I could find 1 3/4" threaded all the way to the head, this would allow a little more bolt to be past the nut.... Maybe a real hardware store would have them, I'll keep looking.
Notes: Like in a car, loosen the lug nuts/wheel bolts before you raise the rear end (or you can set your brake). It's easier to see if a lug nut is working loose than it is to see if a wheel bolt is. My front wheels are not loaded, so they're easy to put on with the stock wheel bolts.
I apologize for the lengthly explanation. It's really easier to just play around with the procedure than it is to explain it.
I won't take total credit for this idea. I saw a picture of a Kioti done this way, which inspired me to try it.