The 16 1/2" Wintec is better on a 14.2, really, because of the flap size. It'll fit on a smaller pony, just looks big.
The newer model tree (post 2010, I think) is a lot flatter. US Welsh ponies are a bit different to those over here. If you had an import I'd have said it was probably a Section C and a Wintec ought to fit fine, tree shape-wise.
The saddle must fit the pony first and if it doesn't fit the rider then they have a problem (where bareback or a treeless might ne the answer).