Only thing I would mention about using a 10mm spacer is that you will need to use longer studs. Unfortunately a 10mm spacer can't just go over your hub and work, your oem studs with make contact with the back of the wheels. So you either shave them down, which I personally didn't want to do, or you go through the hassle of removing them and adding longer studs.no, you said 20mm spacer making 26.5 offset. a 10mm spacer would make your 8.5 wide wheel 36.5 in front which would be about right visually with no poke, I think it'd be flush. the 8" front wheel in back is going to work just fine squared. and that 36.5 offset in front with the 8.5 rear wheel will make a squared setup with that wheel work. however, that said, unless you can find a used set of oem wheels you are going to pay through the nose they are way overpriced new.
I also did additional testing with a 15mm spacer all around, I will get pictures for you later today. While it sits better than the 20mm ones, I did notice when I got up to speed 75km+ my steering wheel would have a slight wobble to it. I am sure I installed everything right, I even double checked the next day and this happened. I have decided that I will eventually sell my OEM wheels entirely and just buy a new set for the winter and one for summer.