Never had an issue with JR 4131's, 8231's, 2721's, 8411's and 8611's.
We tend to way overpower the surfaces on our jets. I've read the servo charts that state this much torque required for this size surface and blah blah blah with big fancy equations etc. When I look at real world applications and the servo's we used to use on jets, or pylon racers, or whatever, the torque is far less.
Now having said that it won't hurt you to use more torque. Tom Cooks original Firebird uses 8231's on the ailerons, in the meantime, if you were to ask on this forum today what was needed everyone would tell you 8711's or better. My very first Kangaroo used one 8411 on each elevon. Never had an issue. When the composite one came out people said 2 8611's for the split elevons when it's likely that even just an 8231 would have sufficed.
So what am I saying? I'm saying that sometimes, we spend money on higher end that is completely unneccesary. I agree that I would never cheap out on servo's in a jet, HK servo's will never find their way into my shop for fear of the sh*tty rubbing off, however, I would never spend the extra money for an 8911HV when an 8411 will work perfectly fine in it's place. The firebird is one of if not the fastest conventional jet around still. It has a full flying stab that is very large and that stab is moved as one piece. One servo does all the work. That servo is only 278oz/in @6volts but it is more than enough. Tom designed the stab around the multiplex (now hitec 5765 servo for the bullet proof gear train. If you were to ask again in the forum today, people would tell you that you need 2x 8711's for that surface. So you spend $300 on 2 servo's where one $100 servo does the job.
My personal opinion is buy the BEST servo you can for the intended purpose. I see digital servo's being used on retract valves and brake valves. That is money foolishly spent.