No, I haven't used a load calculator. I'm very much belt-and-suspenders when it comes to surface deflections. I will use a larger servo than the absolute minimum.
The only time I can recall seeing the effect of a servo overloaded by airloads was an HS-81 on a rudder on a 2M electric, which stripped in-flight right at the top of a 1000' cllimb, leaving me with only elevator to get the plane back. With good use of stalls and loops, I did that.
I had a small electric fun-fly which used dental floss for the pull-pulls. I found out dental floss stretches under load, at speed....
Nice loops at slow speed, flew into the ground wings level at high speed.