I recently modified my MFC for the NE8FF Neutrik/Ethercon adaptor, too. Not too much different from what others have done, other than I attached mine permanently to the back of the unit rather than do the velcro thing.
First, the Neutrik adapter gets some 1/8" holes drilled in it
Then, I drilled and tapped a couple 6-32 holes in the MFC and attached half the adapter shell
And there it is. Nice and tight. Take a hammer to knock it off.
My concern with the velcro was that if somebody tripped over the cord, the Ethercon cable adapter wouldn't be much help - the velcro would let go and the stress would still be on the RJ-45 on the rear panel, which likely wouldn't take it.
I would rather have done something like what the original poster did, with a panel-mount Ethercon connector, but I didn't like the idea of tacking on the cable internally to the solder pads of the existing panel connector. If I was going to go that route, I'd have removed the existing connector altogether to free up those solder pads so I could go through the board with the wires. But, my laziness knows no bounds, so...