I think she would work out on shorter rides. I also have a non typical horse, a huge 16.2 OTSTB trotter that racks like nobody's business (not the speed racking, which I'm sure he could do, but we do mostly a nice forward rack for trails). I have a double whammy, a big horse and in a region of the US which feels like a horse desert, I can't find any endurance or LD rides and only 1 Competitive Trail event a year.
Thanks everyone! Idrivetrotters, a lot of the rides around here are mountainous so I am hoping the cooler temps + her muscling will work to our advantage (she is the ONLY horse I tried out that didn't lose her steam going uphill). However I will probably steer clear of more southern (ie hotter) rides unless it is the middle of winter. Incidentally I also acquired a paso fino mare around the same time that I was hoping to use for LDs but turns out she has prexisting laminitis so I am waiting to see if this can be resolved before I consider her a real "prospect".