Ive never seen it done, but its worth a try... the only reason some people say it can't be done is because they arnt normaly a fast, quick turning breed... and they arnt hot blooded... im not saying its going to be easy, but its worth a try!
Go for it girl!! I was leasing a TWH and he was AMAZING on barrels! He just LOVED to run, and even though he had long Walker back he was able to turn comfortably. He made up for the slightly wider turns by being fast in between the barrels. He was an amazing, versatile horse. Walkers are great. =)