In my opinion, regarding Stamford Bridge Battle, I think the battle was a little further upstream at the Buttercrambe crossing, 8miles straight from York. Theres also ancient road crossings of the Derwent there. A 'Mott' is shown on the ordanance survey maps there, just south of the crossings, on the high ground above the river.
There is importantly a well known'Royal' Saxon Estate 'Aldby' with possible a Large Royal residence or Hall present in 1066, just across the river. This would be an ideal place to await a meeting, especially for a Norwegen King.
If the Mott is 'Norman' why would they build defensive earthworks there , could it be an early mott, built shortly after 1066, as a result of what happened. Also there have been a part of a Anglo-Saxon Hanging bowl or cooking cauldron part found in the fields, as well as what could be a sword scabbard found in the fields South West of Skirpen Beck, directly North of A166.
It is only about two miles further upstream from Stamford Bridge, and the only reference is Stam Ford Bridge, ie the 'Stone Ford bridge', meaning the place of a Stone ford and bridge, ie two crossings. If there were thousands of troops, it would also be included the overall area of the battles there. I think the Buttercrambe crossings fit the descriptions a lot better than todays Stamford Bridge.
I think the 'stone ford' ( Stamford ) could cross the 'Barlam/skirpen' beck, and the 'Bridge' near the stoneford, the Derwent, both water courses connect there. IE the place of 'Two' separate crossings one a stone ford (a weir ?)and the other a bridge. In Late September the ford may of been impassable, but the description remains.