Wintec's don't fit every horse, in fact that fit very few. Generally fat, round ponies without massive withers.

Try getting a saddle fitter out, they may be able to add some packing so have it sit better. Unfortunately I don't think there is a great deal that can be done here though, new saddle may be the way to go. You can pick up second hand, good quality saddles for pretty cheap on Ebay and some saddleries.

I would try a Kieffer - they tend to be good for high withered horses as the pommel is cut back.

 

First of all I agree with calling a saddle fitter out. Second, if he's high-withered AND wide I'd suggest to look into Thornhill Vienna. It's in med range price-wise, designed for wider horses, and seems to have a good clearance (my paint has rather high withers too and she's on wide side). Of course it may or may not fit him - you never know. Another brand for wider horses is Duett (and Black Country, but it's a pricey brand).

 

My Friesian cross has a tad over 8.5" gullet. I have a wide stock saddle that fits, but finding off the shelf saddles that fit can be a challange. I like troopers (better weight displacement) and had borrowed a friends "wide" Tucker Trooper, but to Tucker wide = 7.5" so it was to narrow. Ended up getting one custom made and it had to be widened slightly as she did get a little wider than the initial fit which was about 8". Add to that the short back and finding a saddle that fits can be a challange.
It is a challange fitting horses that are larger than the standard light riding horse, but not wide enough for most of the draft saddles (which tend to have about 10" gullet).
I even went to some custom saddler makers that didn't take the job after getting the measurements. However there are people who make saddles that fit.
Good luck.