Ummm... Sulivan Goldenrods ARE a type of "Ny-Rod" They are a nylon pushrod. Same temperature expansion as the Sig rods...

Its the way you SUPPORT the rods. If you clip off the sheath right at the place the rod exits the fuselage, and bend the flexible nylon back to the control horn (about 6 unsupported inches in a 4*60) and then have the little 2 inches of metal at the end (clevice and short bit of threaded rod) You've got a substantialy curved, unsupported section of nylon. As temp changes, the flexibilty of the nylon changes, and it assumes a different arc. The arc change may be small, and make a HUGE difference in the control surface position.'

The nylon rod isn't shrinking and growing... its bending.

Support the nylon by having wire in it... (or end the nylon at the place the rod exits the fuselage... and use wire from that pont on) and... no major trim changes with temp change.