I 've had a lesson today, took off the saddle pad after that and put the saddle back on without it. The girth is tight but not "ready-to-ride-tight".
As you can see, the fit isn't bad at all. The panels are nice and short, the iron is wide enough (could be widened if needed). It sits nicely behind his shoulder and there is no slipping at all. BUT, I think the deepest point of the seat is juuuust a tad to far to the back. It should be in the middle of the seat or even better just a tad in front of that. Big deal or not?! I don't know...