I'd be willing to pay 20 for a stamp to go towards PLOTS. I also like the sign in system too. Might not be asnbig a deal finding places to hunt if all would show some common courtesy too- pick up trash, hulls, wads, etc... I think most here do. Most of the PLOTS I hunt are for waterfowl and some upland hunting, very seldom do I encounter other hunters so I am not sure what effect the stamp would have. I also find a fair amount of un posted land, I use resources to figure out the owner and nearly all are a trust and the few that show a local owner we make an attempt to contact just in case, more often than not it is "well is it posted? No. Then what are you waiting for/bothering me for."
Ohio used to have a hunting with permission only sign that marked property landowners were willing to open to hunting, pretty sure it fell by the wayside, but it was nice to have and it helped build trust and relationships. Getting permission in Ohio on private land now is harder than getting Kim Jung Un to not get all the votes in an election.
I feel pretty fortunate to live now in a state that has so many options for hunting and hopeful that we can keep jackasses with no respect for landowners and private property from ruining it.