What's too big of a load ?
Will be hauling lumber this spring, the main trail is "groomed" with one long steep hill (about 1/2 mile in length).
How many lbs of material can I haul behind a tundra II?
I haul loads of about 900 pounds of firewood and lumber behind my Skidoo Scandic 500 fan with no problem. We don't have any groomed trails up here in NW Alaska so I can not comment on that. A lot had to do with do you have a paddle track (helps a bunch) and what kind of sled are you pulling? We haul hand made hickory sleds and when I really have a huge load I pull a flat plastic sled from Northern Sled Works. 10 feet long and I stick loads way over the back. Easy to pull even in heavy snow.
Northwest Alaska Back Country Rentals
33 miles north of the Arctic Circle
I've had wide track troubles on the trail and had to do freight sled recovery with a Tundra II. They'll haul impressive loads if the traction is suitable. The Tundra will struggle with heavy loads on hills or in soft conditions. It'll run out of ponies. It'll also beat you up while hauling heavy loads in bumps because the Tundra is so light. I can remember pulling one full 55 gallon drum easily. At two drums the load pulls okay but the weight makes the trip less comfortable since the load will tug the Tundra around. I've pulled 5 drums on flat ground but that was no fun at all. Pulling loads is what everybody thinks about. Don't forget you'll also need to stop those loads.
The answer to your question will depend on traction conditions and the quality of your freight sled. You'll find your happy medium where you can pull a load and still have fun. That's always better than taking too big a load and struggling, but it took me a few years to figure it out. Heavy loads not only get stuck but they break things. You may be able to haul bigger loads to the base of the hill and ferry smaller loads from there. You'll figure out what works by trying what doesn't. That's how we learn.
I can't provide any specific loads as I've never run that model sled, but here's a tip to consider. It's worked very well for me in the past.
Get a buddy with a higher HP sled to go along and not tow a load. On uphills that may be too much for the Tundra alone, run a long tow strap from the other sled back to the Tundra and use both machines to get up the hill. On a significant downhill run, reverse this by putting the other sled behind the load with the tow strap from the rear of the load to the front of that machine. This gives you the ability for rear braking to keep the load in check.
We once made a run with 4 machines and 2 freight sleds over about a 20 mile run on poor and hilly trails. Mid trip one machine broke down and we actually had one sled with both freight sleds tandem behind it, the second sled towing the broken machine, and the last sled running the power line for getting up the hills. Took a long time to finish the run, but we managed. Without using the doubled up tow sleds on some of the hills we never would have made it without a lot of sled and cargo shifting. As it was, we were like a freight train with 2 engines and a row of box cars behind. Note, the driver of the second sled must have a very good full face helmet!