I've run one quite a bit with a venturi,  front NV and tongue muffler. The muffler is an RSM one for a Fox .35, and the venturi is .257" with a .156" spraybar through. Nice engine, tho if you're inclined to take it apart...resist the urge. Like a Fox, you have to be careful with assembly, or you can put a bind in it. I haven't run mine in awhile, but Magnum's directions were to start break-in with at least 20% castor oil fuel, which I have done since on all engines, with no regrets. Adding 5% Klotz for detergent action would not be a bad thing. I noticed that newer Magnum instructions request a fuel with "at least 20% oil, some of which should be castor". Probably because customers couldn't get fuel suitable for the earlier instructions at the LHS. I would suggest 10-18 with castor oil added, if that's what you can get. Castor from the motorcycle or go-kart shop, or even the drug store.

I usually ran my XL .25 on a 9-4 Taipan, but would suggest trying a 9.5 x 4.5 APC. It flew a Pat Johnston "Stunt Trainer" quite well...about equivalent to the Shark 402 kit, Flite Streak, etc.  Steve

No, never ran a 9-6...or 9-5, for that matter. If you want it to go fast, that would probably make it so. Most are not that keen on fast for stunt. You might try a 10-4 APC or other good quality plastic prop (Cyclone or Graupner). The MA Scimitar might also prove useful. Use whatever gives you the best line tension and correct speed.

Sorry I can't help on the rpm, but would expect 10k or higher...possibly 11k+. I hadn't yet found a tach that worked when I was first coming back to flying with engines. Also don't recall the starting qualities, but expect it will be good to excellent when you find the right technique. My Magnum XLS .36 did 4 officials this last weekend with 4 finger flips of the prop, and it has done strings of 7 or more in a row on officials...including one without the battery attached, so be careful in hot weather.  They like to be pretty wet, and would expect the same. The Thunderbolt idle bar or Zinger idle bar will work well for you...both made by Ohlsson Corp. in USA.  Steve