Sorry for the delay, ... thanks for your answers
I'm surprised you didn't have the brace, I had read that it was a necessity for the heavier machines, but if you're not feeling vibration or having issues with the stability, that's good to hear.
My cats aren't terribly big, just under 7 lbs for the 16.5 year old and 12 for the 14.5 year old. I worry about the take off and landing mostly. Having been the landing pad and the runway a few times, I know that there's a lot of force there.