Why would a linkage stopper make a pushrod bend? 

Try from a manufacturer of springs. He'll probably give you a small length free. Worst case use a 2 mm cycle spoke - but that's not very hard

The rudder performance dramatically increased after I put the pushrod through the hole nearest to the rudder. I did the same to the elevator too. Tomorrow I shall check the difference when I fly the same.

Further I checked and found that Robu was selling pushrods: https://robu.in/product/d1-2x840mm-z-type-push-pull-steel-rod-for-rc-aircraft-aero-modelling-2pcs/

Wonder if this is what you are talking about.

Further how different this would be from the rod that came with the airplane?

Be careful about increasing the elevator throws! If the plane is flying OK, leave them. Otherwise you might go out of control

The Robu pushrods "read" good. Haven't used, so can't really comment. They are 1.2 mm diameter. But if hardened spring steel, should be OK. Can't comment on the original pushrods - may be 1 mm SS

This may be a better choice - if the length is acceptable, and will fit in the Linkage Stopper

https://robu.in/product/d1-5x120mm-z-type-push-pull-steel-rod-for-rc-aircraft-aero-modelling-2pcs/

@adel,

A few suggestions:

1. Check if the linkage stopper is free to rotate on the servo arm. In your case it doesn’t seem to be. Enlarge the hole in the servo arm very slightly, so that the linkage stopper can rotate a bit. If necessary, unscrew the bottom nut a few degrees. This will prevent the flexing of the pushrod near the servo.

2. Make sure the sleeve through which the pushrod passes is anchored at 2-3 points. That will prevent flex along the length of the pushrod.

3. Remember that (except in 3d) very little control deflection is reqd for smooth flying.

@Mr Iyer

1: My linkage stopper is fixed to the servo arm. In fact I used epoxy to fix it 'proper and tight'! I did this as the nut below kept falling off. If the linkage stopper needs to be free to rotate (that means a bigger hole) I wonder how would it stay connected to the servo arm without the nut below not being full tightened?

2: I fixed the sleeve well and proper to the carbon fibre rod passing through the fuselage. Now that it is fully sealed I many a times wonder what if I ever need to have access to the inside for some job the kinds that you mention above.

Many thanks once again for your inputs. I have learnt a lot from the same!

Or a drop of cyano (super glue)

The linkage stopper MUST be free to rotate! Look at the geometry when the servo arm rotates

Thanks. I understand your point. Shall order some linkage stoppers and connect them as you suggest.

Why do you need new linkage stoppers?