Not tried measuring inside of pommel will check that tomorrow!
But if i remember correctly the offside is smooth even pressure, but the nearside isn't quite as smooth. Also I notice when riding his back of nearside shoulder seems closer to the saddle than the offside? So I'm guessing you could be right in saying the saddle could be dropping a bit...
I'd like to have it flocked adjusted but it's hard to get saddlers where I am, hence why thinking of a shimmy pad to test for a while.
He goes fine in the saddle, no problems, his right lead is his bad side so hard to comment on the strike off as just been sticking to walk/trot work the past few months