I would agree that 9101's are enough provided that you use one per half. When going to a system of driving both halves with one servo then you should be up into the 60 oz in and higher range.

In an interview I saw with Christophe Paysant Le Roux at the '99 worlds in Florida, he was using one 9102 wing servo with an MK bellcrank to drive the elevator (both halves). That servo on 4.8V (which he was also using) only makes about 40 oz in torque, and he won the worlds with that That would probably be good enough for most of us

9102's are also commonly used to drive ailerons.

The 9101 is pretty similar in power to the 9102 so it will be ok.