Jeff,
Good start to revising the AMA Pulse Jet Rules for RC Aircraft. I started this myself several months ago but life got in the way.
A suggested change would be to reduce the 50 flight prerequisite with a high performance model to 100 MPH; the same as for fixed wing turbine models. Also include a statement that the HP model be flown at this speed and just not capable of this speed. As an example a Diamond Dust delta can easily achieve 150-175 MPH with a racing 40 size glow motor but can be flown with a 19-size motor at a very leisurely speed, far less than 100 MPH. The word capable is the hooker here. A statement that the model must be flown at 100 MPH or greater would satisfy this requirement.
You should also stipulate that one (1) of the availble fire extinquishers be water-based to handle any brush or grass fires resulting from a crash or off-field landing.
Finally, some wording on incorporating heat shielding (ceramic blanket, etc) to minimize the effect of engine heat upon the airframe and RC system.
I look forward to your, and anyone else's comments, on this.
BTW, I submitted my Pulse Jet Declaration to AMA HQ back in Feb 2014 and have not heard back from them on this. What happended is anyone's guess.

Rgds,
Art ARRO