Hi, I just finished building a Seniorita myself. Look for my photo gallery. So far, I haven't maidened yet. Still waiting for the good weather and an instructor to show up at the field at the same time. Soon; I can promise myself. [8D] I chose to go for a 4 stroke Saito 30 and I've had good fun breaking it in!
I don't think I'd worry about being too particular about the servos. There is tons of space in the fuse and wing. I used Futaba 3004s all around, just because they came with my 6EXA TX. I used a pair of 3004s, one for each aleron, with a Y cable. Everything fit easily. I would not recomend using the 1/4in sq balsa for the rudder and elevator pushrods as Sig shows on the plans. I replaced mine with 1/4in basswood dowels because the balsa vibrated badly and was prone to bend too easily. When it came to balance it, With my engine, I had to put the battery and reciever behind the servos and no extra weights were needed. Keeping in mind my engine is mounted a little farther forward than a 2 stroke due to the carb location.
What else would you like to know?