On smaller models (.46 and under) I use the same type of setup.
However I use a Sullivan 2-56 steel rods and the red outer nyrod
tubes. The key to this is to take some of the yellow inner nyrod
material and use it to bush the metal rod. To do this I take a small
section of the yellow inner nyrod and drill it out with a 5/64 bit
( I think that's the size anyway), then I cut it into 3/16" sections and
slide it onto the metal rod, spacing them about 2 inches apart. and
about 2 inches from where they would exit the outer red tube.
I then put a tiny bit of ca between the yellow inner pieces and the
metal rod, this holds them in place. After the ca dries I then insert
the metal rod into the red tube and make the appropriate measures
for fit.
Also the red outer tube must be secured along it's length (at the very
least in the middle and ends).
The bushing of the metal rod takes the play out of the pushrod.
This works well for me, hope this helps.
Jerry