Go over to www.iceshanty.com
and find the forum for equipment and you'll see some good ideas for making a sled. Ice fisherman are worst than duck hunters when it comes to hauling gear out that they don't use.
Get a pair of skies and mount the tub right on them. They will stay on top of the snow and ice and lightens the drag. I used old water skies that I cut down and mounted a cement tub to it and can carry 2 dz. shells in it. The only time it gets rough is when the snow gets over a foot deep.