I did this mod a year ago. 9k miles of charging without issues (maybe 200 charges).
One variation: when I did the mod, I didn't have a resistor to substitute for the temperature sensor. Radio Shack is long-gone, and I didn't want to wait for mail order. So I kept the old 5-15 plug's temperature sensor wires connected to the EVSE. (I removed the other wires, and also trimmed-off the three metal prongs with a Dreml).
I made one other mod: inside the EVSE, I extended the small Control wire (which normally runs from the EVSE to the J1772 connector) to a dual-gang switchbox containing an ordinary lightswitch, and a mechanical timer switch (12-hour Intermatic). The Control wire is connected to both the switch and the timer in parallel. Turning the switch "on" closes the Control connection... as does twisting the timer.
This lets me limit charging to about 80%: at 12A 240v, the EVSE adds about 10% charge per hour to my 30kwhr battery. So if I am parking the car with 40%, and want to stop charging at 80%, I'd twist the timer to 4 hours, then inside the Leaf, hit the timer-override ("clock") button on the dash, and let it charge away. When the timer clicks-off after 4 hours, the Control circuit is interrupted, and charging stops (it's as-if you had walked to your car and pressed the thumbswitch on the J1772). For charging to 100%, I close the on/off switch, and then I let the car's normal charge timer start and end the charge. In practice, I use the on/off switch to charge to 100% all winter, and the 12-hour mechanical timer to charge to 80% most of the summer.
With a dual-gang box connected, it's not very portable. If you wanted it to be portable, I'd put a quick-disconnect between the timer box and the EVSE, and jumper that closed when travelling.