Not to disagree with Jim, and I too have flown the Blue head in Pattern and sport RC, a great engine. About 6 years ago I had Byron Baker rework two of my blue heads for stunt. I wanted to try 60 size stunt, I had them, and I didn't have the preferred ST 60.
Anyway long story short, they are heavy...about 16 oz with tongue muffler. One of them ran well, nice 2-4 break and I flew it for 4 years. The other was plagued with run away issues...but I think it had more to do with the airplane cowl ducting, then the engine itself...but I then started flying electric and never tried to work out the bugs.
It depends on what you are looking to do, if you want to fly open at the NATS....definitely not your engine, if you have one, put a venturi and a ST needle and give it a try.
If you have to buy it....I would buy something else.
Tim