Kojak41, Your Magnum XL .52 RFS, like the Thunder Tiger F-54s, should actually weigh less than a typical .46 2-stroke ball-bearing engine. Your Magnum XL .52 RFS only weighs 15.7 ounces, the TT F-54s weighs 15.2 ounces, where as the O.S. .46 AX weighs 17.2 ounces. This weight is typical of most .46 2-strokes - Magnum XLS .46A 16.0 ounces, Thunder Tiger Pro .46 17.0 ounces, Super Tiger G-45 18.5 ounces, GMS .47 16.75 ounces, Tower Hobbies .46 16.9 ounces.

If your Kaos was nose heavy with a Magnum XL .52 RFS on the nose, you would have needed a plain-bearing engine like the O.S. .46 LA or the Thunder Tiger GP-42 to allow you to mount the flight pack battery in a forward position. A ball-bearing 2-stroke from most of the available manufacturers would have thrown off the balance even more.

Also Kojak41, you mentioned all of the problems you had re-routing your throttle linkage. The carburator on your Magnum XL .52 RFS (as with most 4-strokes) is reversable, you can rotate it 180 degrees so the throttle arm is on whichever side of the engine that will work best for you. You spent a lot of effort rerouting your throttle linkage when you could have simply turned two small screws and flipped your carburator around.

Because 4-stroke engines have rear-mounted carburators while 2-strokes have front-mounted carburators, you may have to run the throttle pushrod past the throttle arm and then simply put a "u-bend" in the rod to turn it back toward the throttle arm. This will allow you to use the throttle linkage included with the ARF without cutting off the end of the control arm too short and creating a binding problem with the throttle control arm at the firewall.

In any event, chopper man, good luck and good shopping!