I used a Futaba 9650 (50/62 oz/in 4.8v/6v) on the elevator on my Calypso (7.56lbs with a YS-61 usually at full power ) and I wasn't easy on it. Worked great. The plane came with JR 507's (40 oz/in-ish, only 537 servo listed) on the ailerons and I didn't feel like changing them before I test flew the plane, and they worked. They're a bit old and "rusty" but worked well enough for the weekend. 9650's are on the replacement table already. I had overkill on the rudder, as I grabbed a servo, screwed it in, put an arm on it and noticed it was a 9151... oops. That's my 2M rudder servo, but it was on the bench and standard size. 9650 is also on the table for rudder along with a 3155 for throttle to save more weight. I think if you go with digital servos, you probably don't need full size servos, depending on torque and what you are willing to spend.

Looking good so far