I have done it. I have had 3 failures with the Bisson on other motors as they are a poor construction and the only reason I purchased this was a package deal and there was not an alternative at the time.It would be major construction to fit a pipe to the Ultimate. One bisson only lasted 3 flights even braced. I reinforced it and rewelded it and it has lasted much longer.
I am still impressed with this motor and will examine my starting procedure etc.