Robert:  Make up a couple of Test Props from a TFSM 9-6 blank, cut  to 6, 6.5, & 7" diameters, and BALANCED, with 'square' tips, for our current 10% Nitro fuel.

  There is  a    >>>>  "LOT"   <<<<    than can be done to this engine, with 20-20 hindsight, to make it more competitive...!!!! (almost everything 'can' be modified!)

   S.T. only made 2 sleeve timings for this enigne, FF & "B" Speed, and you want the latter if you're using a full-length Tuned Pipe. The FF one has a lower Exhaust port, and will work with a Mini-Pipe.
   You also need to make up a 'trombone' (sliding) headpipe, with @ 1~2" of adjustment, to adjust the length of your tuned pipe for test purposes.

 Pipes to use are the 'old' ROSSI 5 cc pipe,  if you can find one, or any or the larger 3.5 cc NITRO (bigger volume)  Straight pipes for the R/C Boats,  WITHOUT the 'muffler' section...     You will have to make up the necessary,  correct headers, and stinger pieces on a lathe, from aluminum.

   Header ID's @ .500~.562"... Stinger ID's @ .250~.300 x 12 Dia's. long

   Start with pipe @ 9"  from the Glow Plug to the biggest diameter of the pipe, and the 7" dia. prop.   Run first WITHOUT THE PIPE, and then WITH the pipe, and record both numbers.  You can then gradually shorten the pipe to get the maximum RPM's your engine is capable of.
   Repeat procedure on 6.5" and 6' diameter test props, and record readings.

       CHANGE ONLY  >>> ONE<<<   'VARIABLE'    AT A TIME!      RECORD ALL READINGS..    USE A 'WEATHER' STATION LIKE THE DELTA, OR THE HAND HELD (CRS?) ONE FOR ATMOSPHERIC CONDITIONS.
   START WITH AT LEAST .012~.015" HEAD CLEARANCE, SO YOU DON'T BLOW PLUGS...USE A GOOD TACH.. THE ONE THAT TNC USED TO SELL IS THE BEST I HAVE FOUND.

  ANYONE REMEMBER WHO SELLS THEM NOW...?  PRICE....?

    You should be getting anywhere from 1 ~2,000 RPM increase, when you put the Pipe 'on' the engine.  As the engine gets further developed, and higher Exhaust timing, this increase will get bigger, as will the peaking speed on each prop. 

   Using a "TORQUE STAND"  DYNO like the wooden one that AMERICA'S HOBBY PRODUCTS of Reading, MA  sells for @ $135. is another USEFUL product to determine the actual HP being generated. 

    Cheers, Glen