Don't think it's the record, but I did 435MHz in the compac solo pool club's 24 hour stock stick over-clock contest that won (I actually let it run for 60 hours before I shut it down).
As for a challenge, I see where there may be a another contest coming up...
I would be up for a contest.... Mine is plugged via a Hub into an Antrouter R1. Best reliable speed I have is 375MHz, at 400MHz ir runs but does not give the correct increase in hash rate so some work needed.
Rich