I dont have the high withered variety but have the T4 cob on Bodey, it's a fab saddle. I would have a look on Ebay if I was you, always a few on there.
Yep, mine is used on a 16hh Section D, as the Wintec that I was using, if I adjusted it wide enough for his body, it was too low on his withers!
I think we could have got away with the normal T4 though, as there's more than enough clearance with the high wither. He was right on the border between normal and high wither on the template.