Do I need a lift kit to upgrade my TM to 15s?

I aquired a 2007 2720 SL this winter. I need to find out if I need to add a lift kit to my TM before going to 15 inch tires and wheels.

My Dexter Axel has " 69 47 HD 198 " printed on the arms on both sides. With the trailer up but the stabilizers NOT down the wheel well clearance is between 2 1/2 to 3 1/4 inch all the way around. The dexter axels arms tilt down about 2 inches from the center of the axel.

From these dimensions it appears 15 inch tires would have plenty of room.

I woud appreciate any input on whether 15s are doable without a lift kit would be appreciated!

Also, anyone who got a good deal on 15 wheel and tire combos could point me to a good source for them.

Thanks!