I don't disagree with Andy about Andover Flight Academy-- it's a small operation, and they only have a few instructors. I was patient, and lived nearby, so it worked for me. I thought the quality of the instruction was generally good. I got my TW endorsement in the Super Cub, and then got a Stearman checkout.
When I finally bought my RV7, I based it at Aeroflex and got instruction in the RV with one of the on staff instructors who had RV time. It all worked out quite well for me, but you do need to be flexible.
I have also gotten instruction from Jan Bussel and he's very good, although I dislike the Vernier throttle set up in his RV6.