Help With Baro Install

I'm Going to be ppurchasing a new baro damper. Currently I have a 6" Baro installed but have to much draft. With the baro set at the lowest position, I have a draft of between .07 and 1.2. I'm going to be installing a 8" baro. My current set up is: 6' Flue pipe leaving the furnace, A 6" tee with the baro, and a 90 into my chimney. My question is, should I install the 8" baro in the existing tee or should I install a 8" tee and 8" 90 int the chimney? any help would be greatly appriciated.

Thanks

Chris

how bout a pic?