Sleds are not skis.
Outside foot on the inside (of the turn radius) runner, inside foot on the ground beyond the inside runner.
I made and sold sleds from 1977 until around 1998. Hundreds of sleds. None of them were laterally flexible. The plastic bed toboggan sleds had aluminum cross brace between the rear stanchions. The Aero sleds with plastic tunnel bed, no wooden parts, aluminum runners, the driving bow was a single piece combination driving bow and stanchions made of aluminum tube or rod. Rigid laterally. If you caught the outside edge/runner it could throw you out or off, but only if your weight was high and you did not shift your weight to lean into turns and side hills. The photos show how. Get Down! Schwarzenegger the actor says in a role in the movies.
With a heavy load, a person or cargo, if the sled runners tilt too easily and the load shifts, it will steer the sled beyond/out of the driver’s control, usually in the wrong direction, sideways down a hill or to the outside of a turn. Positive feedback with negative effects can be catastrophic.
I see many photos of sprint races with traditional basket sleds and newer so-called improved designs that have more sideways flexibility than the pictured Aero sled but the runners are in this same position and the outside runner is partly in the air going around corners on the trail. Because dog sledding is not downhill skiing! The ski instructor tells you to lean into a turn, put your weight on the outside or downhill ski and close the distance between the two skis. The sled runners are a constant distance apart and for mushing you put your weight on the uphill or inside runner. In one of the best mushing videos of my collection, 1993 Alpirod, Deedee is explaining this but got it backwards. “Do as I do, not as I say.” If you lean into a turn which runner will you put your weight on?
This is the best way to balance, to be stable around a corner with a sled having runners 50 cm apart (not like XC or downhill skis that you can bring close together) The exception trail condition is side hill (devers in French) on hard icy surface, or worse, bare pavement. I never encountered this condition in all the years racing in USA and Canada and Alaska and Argentina. In Europe I never encountered this condition except a few times on particular corners in Alpirod, but the rigid sled worked fine. If you can edge/cant runners on ice you may loose control when you edge too much or hit a bad spot, or if you count on the runner edge and don’t lean into the turn enough. Only one time, last stage of Pirena, mostly it was demonstration for a large spectator crowd on trail that would not be used otherwise, there were hundreds of meters of continuous side hill in very icy conditions.
The sometimes horrifying trails and conditions in Alpirod did drive innovation but only afterward, around 2000, I tried to get a bit more edging with the sled designs, so rarely was it a problem. Then I found it was the attachment of the brake bar that prevented the few degrees of runner edging that would be needed. Using a larger bushing/hole in the mounting bracket 1/8″ or 2-3 mm larger OD than the pin was all that was needed, not an expensive and heavier ball joint. I much prefer simplicity in design and construction.
Ed Moody was a sled builder and musher who understood engineering. Here is a photo of his smaller model named for his daughter, Roz.
In the Kotzebue sprint race around 1997 there was bare ice on most of the triangle loop trail and strong winds paradoxically seemed to be mostly side winds. None of the sleds worked worth a #!@$. Roxie, Ed Dayton and I stood on the brakes most of the way to keep the line to the dogs tight, otherwise the sled might be perpendicular to the trail. We were so sore could hardly stand up after the race. A slew brake, like a skate edge to bite into the ice, might have helped.