RE: How do you balance your model?
What woodbutcher was implying is that with the metal pushrods, your CG might have changed (Since they are heavier and they are completely behind the CG) So re-check before you fly.
Two things you have said have piqued my interest.
First, you say the engine keeps quitting at idle. Sounds to me like you need to adjust the low end needle valve. It is a small screw in the center of the throttle arm (See pic) The picture below is for a different engine. Yours does not have the "Blue Collar" but the adjustment is in the same place.
Bring the throttle to idle, let it idle for a few seconds, then pinch the fuel line with a pair of pliers - the engine should rev slightly, then die.
If the engine dies almost immediately, you're too lean and need to turn the screw out (CCW) - Note, only turn the needle by 1/8 turn each time.
If the engine revs a pretty good amount, then dies, the low end is too rich and you need to turn the needle IN (CW)
In either case, try it again, and repeat if necessary.
The next thing I wanted to mention is: Once you have the engine idling properly, if the plane still lands fast, try adding a little more tail weight. Not being able to slow down on landing is very often a sign of being nose-heavy.