RE: Extreme Props
Hey there...... interesting post.
First - word of caution. There are VERY few commerically available props capable of the rpms and loads you noted.
When you get over 25K rpm, even in those 1/2A and old QM15 sizes, you want VERY good quality wood props, and preferably carbon fiber/glass props.
Two sources I have handy that may have what you are looking for - will require follow up contact to confirm they have something along those lines.
[link=http://pages.prodigy.net/gcleveland_grsmodels/_import/pages.prodigy.net/gcleveland_grsmodels/index6.html]GRS down in Louisiana[/link]. They are big into CL speed, combat, and generally fast little engines
The other is [link=http://www.supercoolprops.com/]SuperCool[/link] over in Australia.
Look around for other links to CL speed and combat specialty shops and suppliers. There are a handful out there. They all will offer or have links to suppliers for props similar to what you are looking for.
Use great care in modifying props. Be sure what you are starting with has a hub and blade design up to the task. Usually a larger prop. Then work from there (mainly refering to wood props).
There are very few prop driven r/c models that can reach the 200 mph range. Although not impossible, it takes a good deal of power, planning and hard work to get there.