No, never tried trials, but the bikes do look neat. Going to try a bigger rear sprocket (+ 3 teeth) just to see what it feels like, got to add a link to the chain though for that
And I do have another 24" wheel MTB, it has an alloy frame so is pretty light, I would have used it for the stand up but wouldn't be confident doing any welding on it, might be time to try a trials