A trick I learned about peach & apple pie: Sugar/flour the cut slices, then
drain the excess liquids BEFORE baking. I think it was Pam Anderson who gave that hint and it really works...especially for juicy peaches (an oxymoron for my lately). I think it was a 15-minute wait...I'll try to find it to verify.
In the apple case, I've even started pre-cooking the sugared slices ahead of time, drain and reduce the juices, then drizzle them back on top of the slices before adding the top crust. This really helped to eliminate that big air gap you get between top/bottom crusts with apples that cook down a lot.
You might also consider using peach jam to sweeten rather than regular sugar.