I have an aire Super Duper Puma. The spec width of my model year was 5'11" I use 8.5' oars on tight and technical water. On big water or long flatwater I use a 1' extension = 9.5'
the 13' trib has a 6'8" spec, so I suspect the 9.5' oars should work just fine for you.
the tubes are 19", so the minimum frame width you want is where the side frame rail runs right down the center of the tube which = 61" (6'8"-9.5"-9.5"). But most folks like the side rails out side a little farther so a 64 to 66" width frame would probably be optimal.
Bottom line the 9.5' oars shouldn't feel way to long, they will work fine. If they seam a little long after several uses, Probably better to keep the 9.5' oars and look around for some 9' ers, 8.5' will be too short for sure.
The spec drawing for the 13' trib is here to help with dimension planning.
I have cut down carslisle oars (from the handle side) and it is fairly easy to do with a chop saw with carbide tooth blade to make the square cuttoff at desired length, angle grinder with cutting disk to remove the left over oar shaft that is still on the handle shank, screw driver to pry off the oar shaft excess after you score a cut length wise down the excess on the handle, and epoxy to re-attach the handle to the cut down shaft.
However if you are going from 9.5' to 9' you are only cutting off 6". I don't know how long the handle shank extends into the shaft on the cataract oars. On the carslilses the shank is about 5 or 6". So you don't have much room for error when wanting to cutt off only 6"