First I must say that getting a few Manual J's and D's gives peace of mind.

I've been going over the ducting, comparing the design(s) of each. I see that the ducting has a column for TEL. Also each branch is listed as a separate measurement. It's great that this is part of the equation and I can grasp the concept as for why.

So my question is, Due to limited space in the attic am I able to streamline or cut down the length(s) of the ducting as designed? I have no problem with resubmitting a fairly detailed print or drawing of the workable routing and lengths that would result.

I understand that rules of thumb are bad and the Manual D was drawn with the TEL in mind. I even tried to self educate by crunching the room requirements as compared to the branch line vs the trunk line vs the cfm vs fpm and so on.

I am totally pleased with the engineered results but unfortunately it will be a PITA to make this work in my situation. It looks good on paper, but...