In mine, I used 4-40 pushrods too. I use the sheath from one of the gold-n-rods, and use the yellow tubing for a spacer. I cut the yellow ribbed tubing in about 1/4" lengths, and slide them over the steel rod every couple inches (this keeps the rod centered in the sheath and keeps flex to a minimum), then just wick some thin CA on the yellow tubing so it does not move on the rod. This makes for a very slop-free yet rigid setup and has worked well for me.
Dave