I used a regulator I got from Don's Hobbies (US), I wish I kept track of what brand it was. It was on the ignition of a DA 150 (Gas motor). It failed in the off position. If this was on a rx I would have lost the plane.

I have never used a regulator with 6v duralite or nicad and I have not experienced any problems with my JR recievers.

Anyway, if you want to use one, try to determine if it will fail in the on or off position and choose accordingly.