My DraftX-QH wears an 80 blanket and is over 16H
we have the marathon cart made by Carriage Machine Shop
as seen on John Greenall’s site http://users.vermontel.net/~greenall/carts.html
I LOVE this cart - it is fairly light to pull by hand on the ground
it has rear access – which some people hate but Im OK with
I find this cart easier for me to get into than most of the “front” entry roadcarts and with my limited mobility - it works fine
as for size - the wheels are 50 inches, the shafts are (I think) 80 inches long from the crossbar / swingletree
its at least 24 inch - probably wider - at the crossbar
I had to re-position the footman loop
and we put an additional step off the back (for me)
but other than that it went right on the horse
it IS lower than front entry carts but I can still see over his back
for most 2-wheel carts - the wheel and the shaft will get you into a cart the size you need
not sure where you are located but there are usually carts of this type for sale used
at our barn - another PONY driver uses a RunningBrook SPINNER
we find this cart MUCH heavier to handle on the ground than my larger cart - just something to think on . . .