After seeing the install of another members overhead CB Radio, I decided something like that would work for me. My goal was to try to keep mine slightly lower for two reasons. The first one is that I didn't want to have to try and find a way to finish raw ends above the roll bar, and secondly, and more important, I use a spiderweb shade top all spring and summer. I still wanted that to be able to be flat across the top and wanted access to the front center footman loop to tie it to.
I chose to use a length of 1" x 2" x 1/8" wall aluminum rectangular tubing. I found an 8' length at our local "Blue Collar Supply" store for $30. Nice thing about aluminum, is that I can work on it with my woodworking tools. I cut it to length, then used my band saw to shape the ends to fit the roll bar on each side. I drilled a 15/32 hole on each end that a 3/8 x 16 T-nut (without prongs) would drop into and used the same bit to slightly enlarge the existing holes in the roll bar. A 3/8 x 2" Allen Head Stainless Steel bolt was then used up from the bottom of the roll bar. This left a pretty finished surface on both top and bottom. Wound up being very solid. A little satin black Krylon and it's pretty much done except running the wires...another day. Here's some pics.