In the meantime my logistics have firmed up and as it turns out my longest resupply stretch will be 9.5 days – so the packing problem is more like 8.5 days. Pretty much the rest of the resupplies will be no-brainers, so I can go with the traditional "repackaged but modular" configuration I usually use – everything repackaged, but bagged up by days. This is very convenient for grab and go trips.
When I dished out the mula for the Weekender I did so with the conviction that I did not really want to carry more that 7 or 8 days of food if I had a choice, and like having an UL pack this kind of forced me to consider things carefully.
When doing this exercise I discovered that my "luxury foods" – coffee, hot cocoa and electrolytes are what put me over the top. They take up a lot of space if done in the default inefficient individual packet mode.
Anyway, here is what 8.5 days worth of food (~ 3000 cal/day) packet like I have taken for years, very space inefficiently, looks like in full bagged mode(a.k.a. anti-environment terrorist mode):


Obviously the packing method while logistically nice is not good for packing density. The simplest idea was, without changing what I take, was just to further repackage – to take 3 different dinner types and package them in 3 separate loose bags of 3,3 and 2 dinners each. One bag of trailmix for the whole time, and so on. Also to pack all the small items – coffee, cocoa, electrolytes packets, pure carbs, and so on loose in the can. Loosing the ridiculous number of bags as well. That looks like this:

So I got it (almost all in the can). The bag on the outside, again, is just the coffee, cocoa and electrolytes. For the big/long resupply I will again try to loose the variety and just pack 3 bulk bags for the coffee, etc. Still, it doesn't look like it will fit unless I sit on it, or compromise on some things. Basically this result has been achieved without changing WHAT I eat, just strategizing how it is packed, and maybe not having quite as much variety. The latter seems like it will be less important for many days – I think 3 different dinners for example, and 1 type of coffee is probably plenty.
I'm still thinking about changing WHAT I eat. It seem clear I could get a lot more into the can if I changed that. Since I am right on the edge for this trip, and since the only time in question is right after MRT where I can hang, I think I will probably just hang the overflow for a day or so, and be done. My brain hurts and maybe I will switch to worrying about something else.
However I feel like after all this I have very fine understanding of how much I can and can't do working with the weekender, and the tradeoffs involved.