After assembling the gantry kit, there was a problem to solve... how do you route the motor control cables, router's power cable, and wet/dry vacuum hose over to the gantry.
After thinking hard about all kinds of complicated setups, like overhead cabling on a retractable bungee, swing-arm gantries with a couple segments, etc., I remembered something I saw at the hardware store... Carlon ENT Flex-Plus plastic electrical conduit, affectionately called "Smurf Tube" by electricians apparently.
Lowes conveniently sells 10' sections of this stuff for a whopping $3.
Now, you're probably imagining how conveniently all the cabling will fit inside this tube, right? WRONG! The key feature of it that I wanted was that it's flexible, yet mildly stiff. I would say it's about 1/2 as stiff as a fiberglass tent pole. If you take the 10' section with one end in each hand, and put your hands together, it bows up and makes a great arch with enough resistance to support "hanging" cables and hose from it!
So the next thing I needed was a way to attach it. And for a mere $2 each, I found these 1" metal rubber-insulated hose/conduit clamps. I used 4 of them.
I mounted the end of the tubing to the side of the z-axis, by putting the clamps under two of the 1/4" screws that were already conveniently there! I did this first, so that any slack would not be at this end.
I then ran the gantry to the far side of the table. I arched the tube to a position that looked "about right", and didn't put too much tension on the y-axis. This turned out to be about 8'. I put two more of the clamps under two 1/4" screws on the chain mounting bracket. For these, I had to switch to a longer screw (and drill the 1/4" hole a little deeper past the crossdowel).
I then routed the wet/dry vacuum hose, motor control cables, and power cord for the router on the OUTSIDE of this blue tube, and zip tied the bundle together. Be sure to leave enough slack in the y-axis motor cable so that the z-axis can travel up and down without pulling it tight.
There is about 2' of blue tube that hangs off the side of the gantry, kind of like a tail. I've left it in place so far, since it helps keep the cable bundle out of the way of the chains and drive mechanisms.
UPDATE: I recommend you DO NOT use zip ties, if you like the blood in your ears to stay in there. The cropped zip ties leave sharp little plastic blades, right at head level. I have several cuts on my ears where I walked past and caught the edge of a zip tie. Instead, you can get a roll of Velcro wire ties for about $5 for 30. USE VELCRO INSTEAD.
Total, this awesome solution works great for the sum of $15 ($3 tube + $8 clamps + $4 Velcro wire ties)! I also bought an 8' Shop-Vac hose ($20), Shop-Vac hose coupler ($5) and 8' "air-conditioner" extension cord ($8), which I made a permanent part of the cable bundle. Now all I have to do is plug my wet/dry vac and extension cord into the gantry's connections, and go!