Alan
Eddie Batchelor here -we met at your contest at Sparks, I called for rwlewis's dad.
I flew the Explorer(excelleron) year before last with a YS110. This was before the Saito 125 was available.
Althought I really liked the Ys on mine, If I was doing one now, after hearing Tommy S's report on the Saito 125, I would put a Saito on it.
My Explorer was very nose heavy and the lighter engine would be a benefit. I think I had 6 or 7 ounces on the tail of mine and it needed more and that was with the tank on the CG.

If you don't mind some unsolicited advise :
-Start at the recomended CG but DO NOT use their recomended control throws. 10-12mm on elevator and aileron and 20-25m on rudder then fine tune from there. Too much rudder throw and it'l drop the nose with yaw.
- reenforce the landing gear area and wrap the wing joint with fiberglass.
- check all glue joints ( general ARF advise)
- I used the metal hinges and did not have any issues - other have replaced them , your call
- I didn't use any of the stock control horns but I did use the stock engine mount and it held up for 3 years, athough I've read of the isolators breaking down. I purchased replacement isolators at the LHS in your area but didn't use them.

I can't think of anything else at this time. Let me know if I can be of any help. I still have my old one and 1 never built so you;re probably not gonna be the last guy assembling one. But my next one will be E powered.

Eddie
LARKS
DeQuincy,La