I just cut in the gem box line up a long ?" bit and drill a pilot hole, or using a long ?" bit in the hole saw and just drill it out from the inside, then put a EMT connector and a short piece of EMT in the back of the box then go out side and using my cordless sawzall cut it at the length needed remove the burs, install the LB and pipe from there, but since the owner didn't like the idea of opening the walls on the inside, I would make sure he was ok on the idea of running pipe on the outside? I know many do not like things running on the outside of there house, other options are finding a chase from the basement to the attic above the second floor then using fish sticks (?" fiber glass semi-ridged rods to fish in wire with) to pull your cable up to the attic then fish them back down into the wall from the attic, not always possible with outside walls but if you can get them down into a inside wall then remove the base board and put a mouse hole that the baseboard will cover and notch around the room to the place you need the receptacle with another mouse hole, then use narrow nail plates to protect the cable, reinstall the baseboard.
I did a few rewires like this for the National Park service on some historic homes that we were not allowed to damage the inside walls or the outside walls, we had to remove and re-fed all the old K/T wiring with all 20 amp rated circuits, and two of these homes were three story, I had enough fish sticks and flex bits and extensions to reach from the basement to the attic above the third story, but making over $50k+ for each one was worth it, just a pain to do.
