"George Sambataro" wrote:

How much of a NO-NO is it to put supply ducts at the end of the supply
plenum? We could use better air flow at the ends of the house and I was
wondering if the larger plenum with all ducts to the side would help.

Yes and no. You need a larger duct feeding the it to flow more air, and
it needs to be reduced in size as it goes along, to keep the pressure
(?) up.

I remember seeing a laboratory in a national lab, built after WWII to
hold a room full of vacuum tube counting equipment. Talk about a cooling
load!

The ducts were like 2'x4' at the beginning and ran to the end of the
room, and had ducts coming out every foot on both sides, and shrunk by
like one inch after each pair of ducts, until it was just a single 8"
for the last pair. I was there in the 70's and what had been a 6' rack
cabinet had shrunk down to about an inch wide in a rack chassis.

Even in modern houses, I see that, where the main air duct reduces down
in size, after feeding ductwork.