I would try a 11x5 apc. . The 13.25x3.75 or 12x4 will also work well but you may run into prop clearance problems with the PT40 . Master Airscrews are also good if your flying off a rough feild and prop strikes are an issue.
My trainers are all taildraggers with after market main gear and have plenty of clearance for the bigger props. If the feild I,m flying has a tight landing area I switch to a lower pitch prop mainly to help slow it down on landings. 13.25x3.75 works the best and the wide flat blade acts like a brake when pulled to idle. But for an overall trainer prop the 11x5 seems to give enough top speed and also a little more pull for loops and such.