You can use Dave Brown Pushrod's. They are fiberglas, and the ends come in single or double. You can squeeze 4:40 rods in, with a little mod. Getting two 4:40's in for split elevator's will work, if you use that size.
The thread way works fine, used to use that with 3/8' sq. stock. I just looked up at your set-up. Did not realize you were using the long rods. If it works, don't fix it.

Crank