I tried a MagnaFlow with a 2 1/4" exhaust and now have a 2 1/2" exhaust with a MagnaFlow. The MagnaFlows are great for making power but on a Sportage they are loud. The flowmaster should work good and not be as loud. It's going to be hard to get an axle back muffler, the rear overhang is quite short, I would just put the muffler in the stock location and have put on a new tail pipe from the muffler back.

Dennis

95 Sportage, gone but not forgotten.
98 Jeep TJ, 4" Zone springs with RC Long arms, Ford 8.8", 4.56 gears & Detroit locker rear, D30, 4.56 & Detroit Trutrack front.