Pull any and all loose nails. Will chew the shit out of sidewalls. I'd recommend filling the gaps, or only crossing against the grain, even the edge of the planks could rip a sidewall if you drop into it. Probably wont stand up to any hits from the skidplate, so I think you're on the right track. Might build the platform so that you can fill it with rocks or dirt so it's stable.
For that matter, just toss them out randomly on your yard, and practice floating or hopping the tire onto them etc. You could build an expert section if you put the ribbon in tight.
ATGATT: When you fall off your motorcycle, you will be wearing what you were when you got on your motorcycle. Dress accordingly.