Hi.
I quit using the SC10 pin hub wheels on the rear, because I stripped them out under power and ruined them. I don't recommend them at all for the rear.
I still sometimes use the SC10 wheels on the front and they work fine there. (I have a set of stock SC10 tires mounted on them and those tires work well for me on carpet.) I do as you do and set the axel nut loose, so that there is no binding. To help keep the axel nut from loosening up I use some locktite on the threads. Even with the locktite, they will sometimes still loosen up, so I check them every so often and re-locktite them, usually just before the mains.
I may have already sent you this message but it's not showing I did. How did you use the SC10 wheels (without hexes) and keep them from binding on the hubs? I got some but I have to run the axle nut pretty loose to keep it from binding. I will probably stick with the hexes but I was able to get the sc10 wheels pretty cheep so I just gave them a try.