Nice cop-out answer... honestly, it makes no sense. It sounds like you burned a lot of stuff experimenting... alot of stuff for a poor guy. A poor guy with a 2.6m comp arf yak. You could have bought an airframe that's $80 less and had regs, so don't give me this poor boy load of crap. I'm not going to waste my time on you any more. Good luck with your cheap toys.

Shag555,

It's normally not a big problem if there is slack when the rudder is deflected as long as the cables are tight when centered. The rudder is loaded when deflected, and flutter normally only happens around nuetral. I believe the only issue comes when doing a tail slide... if the rudder has max throw, and the "pushing cable" is loose, when doing a tail slide the force on the rudder can reverse and the rudder can slap over and hit the elevator.

The following is only a point of interest for those that care about aerodynamics.

There is a phenomenon that can occur in the C-130, but I don't know if it can occur in IMAC planes. It's called a "fin stall", or "rudder lock". Basically, the rudder is so efficient, that at certain lower airspeeds and large rudder deflections, the sideslip angle can exceed the rudder deflection. The result is that the relative wind switches to hitting the opposite side of the rudder and tries to lock it to full deflection (in the full scale it takes a lot of pedal force and maybe a power reduction to get the rudder "unlocked"... assuming you have altitude since it usually results in the inside wing stalling and a large loss of airspeed). Servos have plenty of power to center the rudder again, but if you have a lot of slack in the cables, when this "fin stall" occurs it would push the rudder against the slack cable and slacken the tight cable. This would cause a sudden increase in rudder deflection and a bump in the yaw axis. There should be no danger of an oscillation since, once the "fin stall" occurs, the sideslip angle will increase further and tighten the rudder lock.

The only reason I bring this up is that I have seen planes (such as mine) that can fly across the field in knife edge at fairly high AOAs with minimal rudder deflection. Luckily with our IMAC planes we have centerline thrust which help keep the pressure on the correct side of the rudder. If a "fin stall" were to occur, it should only be at very low or idle throttle settings, probably in level upright or inverted flight. You would see a sudden increase (or bump) on yaw. As soon as you center the stick it would go away. Much more dangerous in full scale.