Help!

I am installing a Thelin parlour 3000 I purchased last year in the corner of my family room. I want the vent to go straight up through the ceiling and through the roof. The problem is the vent outlet in the back of the Parlour is 2 1/2 inches off center I tried a 3"x4 appliance adapter tee turned 45 degrees and a 45 degree elbo 4 inch. this put me way off center the other way...would a 3" appliance adapter put me closer? .Are there any thelin installers out there that have fixes this problen....Don