rubberized horse stall mat
In reply to your quest for material for your tires to rest on during off season, I have been using rubberized horse stall mat. I take one sheet (4' X 6') and cut it into 6" wide strips several being 2' long , several 3' long( there is enough for 2 trailers here). I simply lay the material on the ground and roll the trailer up on to it.
This mat also doubles as a trailer leveler when camping.
they are a little heavier than most other woods but,
they dont retain water
they dont rot,
they stack easy,
they dont slip when stacked,
trailer tires do not slip off when wet,
they store quite easy in the back of the truck box.
cost = 45$ or 22.50 $ per trailer.
good enough for the horse , good enough for the trailer!