If the pulk is sliding pretty easily, then you are not putting too much extra force on the snowshoe tails. If the pulk is not sliding well, then there is extra force.
Solution: apply Maxi-Glide or similar spray lubricant to the pulk's sliding surfaces.
I was on a SAR practice one time, and the snowshoers were pulling a litter full of gear, but the sliding surface had iced up, which caused a lot of cursing from the snowshoers. We stopped and I applied Maxi-Glide to it, and it was simple from then on.