Re-did mine with the combination of wider two by tens down to two by sixes pressure-treated lumber. They did shrink up a lot but I wanted some gap between boards for drainage just got more than I wanted. Also haven't broken one yet but am a little concerned about how much Bowing I'm getting when I load my tractor on there. I feel the supports on my trailer should've been installed closer together for the use of thes size board. I did break through the ones I replaced. They were installed extremely tight together and rotted out pretty quickly I do not believe they were pressure-treated though.
When comparing the total square footage of the area covered, the lumber comes out close enough to the same that it doesn't make a difference what size you use for each board, the total cost will be the same.
I like to measure the width of the area and use the lumber that will fit it best. I think I used 2x10's on my trailer when I replaced the decking on it a few years ago. That way I didn't have to rip any of the boards to fit.
There is very little shrinkage on 2x lumber. Install it tight and the small amount of shrinkage will allow water to flow through it. The problem with shrinkage is in 5/4 lumber. The change with that is significant.
I am using 2x12 PT SYP, because I had a small stack I got from a job site few years ago, for free. They do Crack more than 2x6. Before that I actually used 5/4" oak pallet boards, from Hardi board pallets; painted them, got about 3 years of life form those.
We get rough sawn ash or oak 2" thick. Its strong and not too slippery. I thick aluminum diamond plate would be expensive and slippery at times. The Amish mill makes boards pretty reasonably.
Kubota M108 FWA loader, 2014 Kubota M7060,Kubota MX 5100, Ford 1500, Kubota Bx25 , Kubota RTV900, Kubota ZD331 Zero turn mower.Kubota B1200 Grey to be restored.
I did my part for re-cycling and managed to get a hold of some flooring from and old Hi-way van reefer trailer, the biggest part was separating it from the hardwood crossmembers and the urethane foam that was used to insulate and seal it all up, once that was cleaned up however it certainly went onto the trailer just fine, some heavy duty sheet metal deck screws and all done. It is very strong and will never rust or rot