Intake duct size: Travis FPX 44

So I'm finishing up the install on my FPX 44. We had the blower (intake) unit mounted under the house, and I want the duct to run to the outside. Problem is, it's about a 28' run. I made an adapter to go over the front of the blower/intake box to adapt 9" pipe. Book says max 15' run for 6" pipe, 25' run for 8" pipe. So I just went with 9".

The chimney pipe is cooled pipe and the intakes/pipe are 7"

So my question is this: If I'm running 9" for the intake, and choke it down to 7" right at termination to the outdoors for a groovy intake that came with the chimney cooling vents (I don't have to use those so I have them left over) am I choking down the CFM needed? I mean, really?

The anal-retentive side in me wants to run the 9" duct all the way through the wall, but I"m concerned with putting a hole that big in my concrete block.

I'd almost rather like to use the 7" intake/vent that came with the stove (this WILL NOT be seen as it will be under my deck) because it's a bit smaller and already set with a rain guard and screen on it.

Am I thinking too much?