My HVAC tech says we have to run an 11" x 26" trunk line the whole length (or most) of the house. I paid extra money to have 24" deep floor trusses (needed to span the entire basement without support beams), but the webbing does not allow 11" x 26", only 11" x 18".

I have posted a link below and have a question. I used a couple calculators online to figure out effective duct lengths, and I don't think there's a single duct that needs to push more than 100 CFM (10' ceilings) for more than 75 feet.

Is there a way to have the main trunk (green in pic) ONLY be run in the 24' 8" section and then run supply only ducts (blue in pic) from there? I think I'm going to talk to Energy Wise this week to see, but I don't want to get my hopes up. I'm quite frustrated that this has happened because I specifically paid more for the floor trusses to be able to not have to hang ductwork from my basement ceilings...

This picture isn't the duct "plan", it's just for an example for my question.

https://drive.google.com/file/d/1x8fYD87aJLMCI2z4wbsZWp1zN7P2YHvy/view?usp=sharing

I don't see why you can't make individual runs to each register. I did this and it is just a lot of ducts/flex to run. I am sure it will add a lot of cost.

Might want to try a HVAC forum....

Energy Wise is the best place for a solution. I've been recomending them for 15 years

+1 for Energy Wise.

11" x 26" seems like a very big duct. I would want to know what is driving that requirement? What about doing small duct high velocity HVAC?

This saga does illustrate why doing an integrated building design/build is important. All to often HVAC is accomplished as an afterthought which can lead to these sort of issues.