I have one, but it's just a diddy pony saddle (but def has the white xw gullet). I can measure tonight if I remember, but not sure if the measurements will still be the saqme for pony saddle?
Right, the inside of the saddle inline with the D rings, is the base of the gullet on my wintec - measures 5.5"
If you wanted between the panels (lower than D's), I measured that as 5" inside the panels...
HTH =]