I used 3/16" carbon fiber tubes from Central. It has wall thickness around .7mm with 2.5mm rod ends.
You will want to use sponge if you can't mount support for it. I pushed the sponge (to the half way between the elevator servo and bellcrank) thick enough to reach both sides and tall enough to touch the top and bottom of the fuse.
Been flying that setup for more than 7 years without a problem. some trim changes between hot summer and cold weather, but not very big for me.