WHY ???? I see no reason to carry less then a full mag .. in fact I carry a spare mag on weak side ..

My Beretta PX 4 is 13+1 so I carry a minimum of 27 rounds and when I cross the river even more ..

If you want something lighter go to a smaller sized weapon ..
something like the Sig 238 in 38 or Sigs 938 in 9mm ..

Another thing you may try is to move your holster 3 or 4 inchs from its present position .. I have found a certain position about 4:30 bothers me but moving it to 5:30 ended the discomfort ..