A couple of pannels should be OK, but bear in mind Hardox is pretty heavy, especially in comparrison to Aluminum or Titanium. But for its weight, youre getting a seriously tough material - Id say 8mm thick of it would probably stop the majority of spinners round here. Also remember very few spinners can attack the top, in which case 10mm Hardox there is a bit overkill. There arent many axes around either, so its probably best to either choose a different material or shorten the thickness there.

Looking at the stats for Sky-Blast, 20mm Ali is probably pushing it too. I highly doubt 80hp is capable with that drive train, 32mph is just too fast and the ground clearence is on the short side. But hey, I always cheat as well so dont take my word for it!