"Food for 2 people for 11 days should weigh ~25lbs.
Total kit for 2 people should weigh ~50lbs."

That seems to me to be a little on the light side for an 11 day trip - I pack ultralight, as light as anyone, and a lot lighter than most.  2008, Food for 2 for an 11 day Quetico trip was 29lbs; canoe weighed 39; that's 68 lbs out of a total of 147, so the rest of the gear, clothes, fishing stuff, whatever  had to weigh 79 lbs.  Carrying 75lbs apiece isn't too hard, though it would be about 50% of body weight, but we still double tripped most portages.  That's for an end of May early June trip when it snowed on the first day - you could get away with not carrying a set of spare clothes and camp shoes in summer, but I can't think of anything esle that could have been left behind, even for a summer trip.

on short portages especially, there just isn't that much time gained by single vs double tirpping - like others, I'd rather make up the time on the water, rather than punishing myself on the portages