Diddly is a 4 year old, rising five in January, 3/4 thoroughbred, 1/4 Irish Draught. He wears shoes, front and back.
While tall horses aren't any more likely to go lame than small ones, horses that have been 'grown up' too quickly(by overfeeding, etc), horses that are worked in weightbearing & high impact exercise prior to maturity(around 6yo) and those who are shod prior to maturity are more 'prone' to lameness. I would be doing only light riding on a 4yo, particularly such a big boy, and I would be keeping shoes off, for a while at least.
If you would like a hoof critique, pictures(as per link in my signature), info on diet, management etc is necessary. I'd also advise you learn all you can about hoof form & function, and effects of different management, so you can make more informed decisions on what may be best for your horse.