$55/cuyd? WOW, this is why we use road base. If you compact it really well it should be OK. If you are worried your mats might be damaged, lay one or two layers of a Geotextile fabric between road base and the mats.
Geotextile fabric is usually available as an under-layer for rubber pond liners, it
keeps the pond liner from being punctured by sticks and rocks. www.farmtek.com Item#105246 Non-woven Pond Underliner
Thanks for the definitions, Jim. That helps me a lot.
csaper58; unfortunately I'm still having a hard time finding road base as well. Or at least a seller of road base who will deliver less than a semi-full. I don't have a truck big enough to haul the ~8 tons I need.
My contractor neighbor may have found a place where I can get what he terms "rice gravel" and can deliver (they're just up the road from me), so I'm going to call today and see if I can go check it out. $7 cubic yard, much more to my liking.
Rice gravel is very fine pea gravel. The same size as aquarium gravel. I don't think it will lock together the way you need it to. Take a muck bucket with you, fill it with the rice gravel, then step into the muck bucket. Stomp your feet around like your stomping grapes, if your feet sink into the gravel it won't pack solid enough to work under the mats.
I'll try that, thanks. I had suspicions that this won't work for the stall, but my neighbor said he's used it a lot as a base for golf greens and that it packs like concrete. I worry that our definitions of "packs like concrete" are different, especially when he's talking about humans and I'm talking about a 1400lb horse.
A friend in BR La suggested you try Construction Aggregate Supply ask for Robin,225-381-1680 They have..#6-10 road base $26.50/ton
# 10 lime stone $26.50/ton
NOTE; 1 1/2 tons = 1 cuyd
youwould just need to find a private hauler wih a small load capacity