I asked my barn mate and she said it is certainly allowed. But, has anyone done it or know anyone that has shown a large pony in the Adult Modifieds? Assuming you need to do the horse strides to pin but the 3’ large pony division is set on a 12’ stride, correct?
I would check the division specs as it typically says Horses in Mod. Adults. With that said I did see a large pony at Katy this month do the Modified Adult Eq. but not the Modified Adult division.
I don’t have a large pony but was just curious because I see a lot of really nice, fancy large ponies and I am pony-sized at 5’3". 
But, I will pay attention to the class specs and see what it says.
I have seen ponies compete in Modified Adult Hunters and Eq in my area (MA/ New England). The specs around here do not specify horse or pony. In my experience, at least in this area, the modifieds are not set at a true 12’ stride even at A/AA shows so the pony does not necessarily need to have a 12’ step. Suitability would be a consideration from a size perspective, but at 5’3" you’d probably look find on most large ponies. The people I can think of that have done it were petite and were perfectly sized for ponies (and on one case a pony that was in the 13.2/13.3 range) and made a nice picture. In the case of the smaller ponies, I have seen people doing an add step and were not penalized as long as the pace/ step were consistent throughout the course (i.e. they did the add everywhere).
If you are thinking about buying a large pony to show as an adult I wouldn’t do it.
[QUOTE=carroal;8014522]
If you are thinking about buying a large pony to show as an adult I wouldn’t do it.[/QUOTE]
This.
I showed my large pony in Modified Adults for a few years, and did quite well. Check your local association specs to be sure it’s ok. When I wanted to move up to the rated 3’ Adult Ammy division I got a horse that knew his job.
Similar experience as M. Owen. Definitely seen this with small adults at local shows in New York/New England and it’s worked out well… I think they typically get the striding but consistently doing the add and putting together a nice course would probably do well - consider that putting together a smooth course is not a given in this division! (my own rounds included ;))
I don’t think any of these adults bought a large pony specifically to show or even really campaigned it, it was more of a fun thing to do and work towards a couple times a year with a pony that they loved riding at home the rest of the time.
I’m in the same boat as you at 5’2" and even showed a medium pony for a full season about 30lbs ago. Its tempting to pick up those super fancy available larges because they may not be suitable for a child/ are still green for less then the cost of a similarly fancy horse. Its tempting but having a large in a non-pony divsion will be an uphill battle!
Even if you have a large strided pony, they will still get penalized for looking more hurried in the hunter ring compared to the horses. Judges may pin you lower and you wouldn’t get the same ribbons you would if you were on horse.
Also consider if you go to resell, your buyers will want a pony who is proven in the pony ring with a child. The market for large ponies want them to have ‘kid’ experience even if it is similar to the adult ring.
As tempting as it is you may become frustrated with your placings/ ability to resell.
