Today I spent some time coming up with a way to add a second conduit without drilling another 3/4" hole in each of the ribs. At Home Depot I found some light weight thin wall 3/4" PVC pipe and some plastic hangars for said pipe. As it turned out, I had to add some mounting tabs so I wouldn't have mount the brackets through the rib stiffening rings. I fabricated the tabs out of some leftover 0.016 aluminum sheet I had.
I attached the tabs to the brackets with some 5/32" dia x 1/4" grip blind rivets from Home Depot. I attached the tabs to the ribs with LP4-3 blind rivets from the kit. I had planned on using two rivets to attach the tabs (photo 1) to prevent rotation, but the large shop head on the 5/32" blind rivets interfered with the rib stiffening ring, so I had to drop the bracket location down about 1/4" (photo2). After installation with 5 brackets, the conduit is quite rigid and stable (photo 3).
EDIT: DO NOT INSTALL A CONDUIT IN THIS LOCATION!!! IT WILL INTERFERE WITH THE W-818 AILERON PUSH ROD. :O(