Isn't it Mike Wills who has hammer boots with big old heels that look like 70's platform shoes? When he has those puppies on, he's nearly 6'4". Adds about a foot, I guess.
(jk)
I think it's mostly personal preference. Mine are mid-height. I think most guys go with whatever boots they happen to have, and modify/adapt as they need to. You definitely need rounded bolts, though, and probably nice wide washers. Several guys out there sell hammer blades, if your budget allows, (Larry Brock maybe?) although strip steel from Lowes/Home Depot or even old lawnmower blades can be used. It's nice if they're purdy, but they don't have to be.
My first blades were about 10 inches long, made from strips of steel I bought at Home Depot and filed to a triangular point. I walked around in them for the first time like someone walking in swim fins. Dave McClelland got an eyeful and hollered "nice hammer boots!" so I took the hint and chopped them down. Later I bought blades from a local artisan, friend and thrower who no longer makes them.
Some guys build up the heels, some bend the blades directly down for an inch or so before straightening them out, kind of like this: (Boot) Z___ . Some do both.
A final point to consider is that you might want to make one blade a little shorter than the other. The short (maybe 1 1/2 inches shorter) blade goes on the right if you're swinging to the left so it can release easier as you turn your body. Again, personal preference.
Good luck with your throwing, Brian-- Frank
"...never give in, never give in, never, never, never, never... " --Winston Churchill
"A goal without a plan is just a wish". --Larry Elder