John I know about reverse voltages, but does that even include when a resistor is in circuit? By the way I was playing around with your curent reg chip with led light strips. Have done about 12 William cars, the light strips throw off a nice light.
The peak voltage will happen in the absence of current flow, which should not happen in a reverse voltage situation. Since the current is limited, it won't kill the LED outright, but I have had several fail after months of use before I decided to include the diode in my lighting designs. None have died since I did that. Since I wire them like they're going to be in there forever, it's a PITA when one croaks, so I don't want that happening. 
I never spend much time worrying about maximum efficiency, the plain diode and resistor are fine for my projects. Typically, I'm running headlights at around 10-12ma, so I'm not losing enough power to worry about it.
Glad the light strips are working out, I just got a couple more spools of them for a bunch of cars waiting for conversion. 
It's amazing how little current it takes to really properly light a coach.
