In my 2003 the front and back bars are both solid tubing. There is no opening into the elliptical piece that connects them. There are small cutouts in the bottom of the elliptical tubing where you can see that the back bar is solid. From the pictures, it doesn't look like your tower has the cutouts, but I would assume the bars are both solid.
If it were me, I would just buy the connector kit from wetsounds and use the old style connectors that connect to the back of the speaker instead of through the clamps. That is what is shown on my old pro80s above. That way you can have the wires come out of the front bar and the speakers mounted on the back one.
Another option would be to route the wires up the back tube instead of the front. You would have to have a disconnect where the leg connects to the base tube if you drop your tower. You might also need a disconnect at the break in the back leg. You would also have to drill holes at the base of the back leg to get the wires from one tube to the other and drill holes at the break in the rear leg to get the wires across the jump. Here's a crappy picture of that option.
Or you could just mount them on the front bar and learn to live with the extra 60s it takes to open the bimini.