Stew,
I've got the tioga 10LA. Tried to put a 10wt. DT Floater on it and had about 25 ft. left over when I ran out of room. I finally put on an 11wt. WF F saltwater taper and hacked about 15 ft off the rear end to get it to fit with about 100 yards of backing. I'm not too concerned about backing in the small rivers I fish with this setup, but anywhere else I'd be looking for a new reel with much larger capacity.

The large arbors are a joke (unless they are the wide spools). You just lose backing capacity and the arbor size of the machined spool could be replicated by putting much more backing on a standard spool.

If you are looking to fish a true spey line you will have to move up to at least the Tioga 12 spey model (I wish I had that for fishing my 11-foot two hander). RA3, Sparky, and several others on the board are much more versed in true spey fishing than I am and can point you in the right direction. I'm just a spey poser who lobs bobbers and jigs with a cut down big stick. But, after using the Tioga 10 for a year I know you'll need more than what I have.