The most important thing to check is that the instructor has suffient experience and it is not going to be a case of the blind leading the blind. I would suggest an instructor who learnt on tailwheel or has been regularly flying tailwheel for a long time, otherwise you will find your self wrapped up in an ever decreasing circle of knowledge. Be aware your Cpl IR drivers might have all the badges but not necessarily the experience, but having said this there are a few good guys out there if you look carefully.