I will dig it out of the bush and get you a picture. You are correct in saying the sleds have a higher psi than the roller but our trails are in very bumpy and uneven country and by not packing the whole trail and leaving some of the snow unpacked, the light drag we use pulls the unpacked snow and dumps it in the low spots where it is needed. We pulled all of our groming equipment with a yamaha nytro and yamaha viper. My buddy did buy tracks for his polaris quad and that helps out alot with the grooming. We do not have a ski club for our local trails, it is myself and a buddy that do all the work and pay all the costs to keep these trails open and operating. We have a yearly operating budget of $0.00 and use our own personal equipment and time. Having heavey or expensive equipment is completly out of the question. Our equipment is what we could afford to build at the time to get the best result we could. It most likely isnt up to the standards of larger ski clubs, or probably any ski club for that matter, but over the years using it we found what works and what doesn't for our needs.
I spend more time grooming trails than I do skiing and my buddy doesn't even ski.