Well my horse is 10 now and he's an italian sports horse gelding (16.2hh).
...Where he's been ridden by novices at the college he's hard mouthed and when schooling he switches off/dead to the leg(completely opposite out hacking).
Id just like some opinions on how to get and keep his attention, how to make him more responsive and less hard mouthed. I want to change his bit(currently in a 3 ring gag) as he's too strong out hacking in it and too lazy for it in field. The more you pressure him to move faster (i.e squeezing more,spurs, little tap of whip he gets assy and stops altogether. He also has an awful habit of putting his ears back and grinding his teeth when I ask him for a more forward trot/extension.
Eventually I want him to do low level eventing...
No matter WHAT you want to do with him, he truly needs to be re-schooled in his basics, particularly impulsion. It scares me to read that he willfully stops when you use a whip. All of that energy will go somewhere, and if he's scared and angry, he is quite capable of bucking and rearing. I don't know how tall YOU are, but my DH noted that when I dismounted his 16'3hh gelding recently, that the stirrup level is 1/2 my height. I've already been bucked off once by a scared animal and when it happened I flew about 9 ft in the air, which broke my humerous and cancelled that year's riding season (2004 experience.) I should add that the horse wasn't prepared for my hobby, and starting bucking when a cannon went off--NOT the norm. He was also 15hh even.
IMHO, please spend the rest of this schooling year and into next spring on perfecting his ground training. He is old enough to give you perfect manners. He should just see a school whip move and respond. MY (now passed on) school horses would respond when my students flipped the whip up--they have excellent peripherel vision you know. School him to move while you stand still, lunging or backing or side-passing. DEMAND that he follow perfectly when you lead, train him to back lightly and for long distances, not just 2-3 steps. It's going to take twice the time to re-teach, but I don't think you can count on him as he currently behaves to keep you safe.
When I was watching a recent Chris Cox episode at a cross country event site, the owners, one of which (I believe he was an owner), was a member of 2 USET's x-country teams and commented that too many talented horses are rushed to perform, sometimes without being taught to stand tied, or other such basics. THESE are recipes for disaster. I'd like to hear about your future success, not your broken arm.