I know lots of folks love neoprene and I've even heard that you can use
then on a galled horse and they will heal as you ride (sounds like a
horse story to me) but I have never had much luck with neoprene girths.
I've been able to use them for months without problems and then ride in
muddy or sandy conditions and find that they get allow a blob of mud or a
layer of sand to form on the inside front underside. This acts like
sandpaper and causes the swelling and scaling in front of the girth area.
The last time I used a neoprene girth we were briefly in an area that
had been flooded that spring and have sandy soil deposits along the
creek. When I untacked the girth had a layer of hardended sand all
along the inside front edge. My horse rapidly developed swollen pouches
and it was a week before the scaly areas were normal. From now on
nothing but mohair string girths.