To all Sig Extra 300XS-soon-to-be-builders....I have 32 loged flights on mine that I built last summer........Run the FPE 2.4, great engine, Futaba S9402 servos on everything, at 6 volts. Still have the stock front wheels, at the current rate of wear, will get 75 to 100 flights before they need to get replaced.
Replace the stock tailwheel for a dubro unit, give the stock foam TW to a parkflier guy. Replace the fuel tank for a Du-bro one, I used the 20 oz, changed the stopper for gas, put a barb on the pickup, AND ZIP-TIE ALL lines!!!!!!! Or else they will come undone. I moved the fuel tank back to the C.G. and straped it in with 2 zipties, with a layer of foam in between. Swing a Bolly 20X10. Do add the clevis to the inner rudder pull-pull wire, but replaced with Dubro's wire (dubro's is plastic coated). Used 4-40 steel pushrods, but soldered clevis and used Sulivan Gold-N-Clevis. Dubro heavy duty control arms work great. Replaced Nylon wing bolts for Metric bolts in steel cap screw, running through a dubro nylon washer, then a big steel fender washer. No glass on wing center, used stock pinned hinges run in with epoxy (Tip, rub some chapstick on the hinge knuckle) I think these hinges are better than CA type, and I wouldn't use CA hinges with a gas motor, too much vibration. I had both aileron servos strip their gears on flight #7, the other side on #15. Since then I sealed the hinge gap on all surfaces. I think either the vibration was causing the servos to fail, or else it might have been flutter. Put in at least 2 1/2 to 3 degress of right thrust. Mine has 3 1/4, and flys right now, perhaps due somewhat to the larger 20 in prop vrs the 16 in that a 120 would turn. 3D flight, elevators are too small for harriers and elevators, wants to snap the plane, but torque rolls, and hovers are fine. Put in as much rudder as you can get, at it will turn on a dime in strong winds on the runway, with the stock tailwheel springs. I was only disapointed that the elevators are not big enough for certain 3D, and was going to sell it when I finished my 33% Extra, but this airplane flys so well, I will keep it flying for a while, and hang it up in my garage when I am done, just for display. Oh yeah, I added 2 bolts to the cowl, and switched them over to metal screws and washers, but left the nylon ones on the canopy. (Remember to drill a small hole somewhere to vent it, or else it will deform in the summer)
My hands are starting to hurt, but I think I covered everything.
1. Seal the hinge gaps with monokote
2. 2 to 3 degrees of right thrust!!!!
3. Steel bolts for wing hold down.( I don't trust a couple-a-grand to a couple of .20 cent plastic bolts, but then again, its your plane, not mine.)
4. Zip tie all fuel lines, and if your stock tank has the metal stopper washer/nut, change it for a plastic one. Trust me.
Good luck, great flying, smooth airplane.