Well, asking how much servo you need for a plane is like asking how much horsepower you need in a car. People's expectations and comfort levels are all different. Some putt along in 3cylinder Geo Metro just fine. OThers aren't even satisfied with a supercharged V10. It all depends on your expectations.

I am sure H9's recommendations are the minimum and will fly the T-craft in just fine in a scale manner. Afterall, this is a scale model, isn't it?

OTOH, this is also an aerobatic scale aircraft of sorts, so if you intend to wring it out in the sky with a big***** motor, then stronger servos are definitely a requirement.