Having run into the same issue of coming out of the back of a wireless and wanting to go into the back of the Axe-FX, I decided to mount my wireless directly above the AFX, and left the bottom right rack screw out of the wireless unit ears. Since the wireless receiver's not that heavy, has a power supply above it, the AFX below it, it wouldn't torque. Then I came out of the back of the wireless unit using a piece of BLACK George L's cable (the thinner of the 2 choices from George L's, called .155), and ran it through the hole so it came out just above the AFX and THEN screwed on the right angle jack, used a BLACK jack cover they offer to hide the silver jack, a small piece of black gaff tape to hold the cable at a right angle so it looks nice and dressed, and from a few feet back, you can't even tell that I have a cable coming out of the rack. I know that's not plugging into the back, but it was the best I could come up with to not have a big cable sticking out of the front of my rack... Hope that might help.
George L's Custom Gear