what are you competing in? Sounds like USDAA? altho I see your in Canada so venues may be different.
I am a competitive person as well, when I enter an agility ring, I go in there to qualify, there I said it (shoot me
I have learned over the years, one needs to look at the dog and what it's truly capable of, not what "I want" but what works for the dog.
When doing Nadac with Jynx, she is just 22", tho we q'd on the higher heights, the speed wasn't there, she was just making time or nq'ing because of one or two knocked bars, lowering her to 20" made all the difference. She was MUCH happier, and well, so was I.
My gsd, was never a bar knocker, she was around 72#, long striding , long legged. 26" was a breeze for her, as she got older and after knee surgery, she would knock a bar here and there, I dropped her back . I could see the effort she was putting into it for "me", but it wasn't good for "her".
There are times when we have to forget about our 'competiveness', (and it has killed me on more than one occasion to do so!), and do what works for our dog..
Good luck with your decision