30-09-13, 10:46 PM
I'd guess it's due to the arc not being in exactly the same position as the high beam filament was. Sounds like you need to experiment, it might be possible to improve things by using either a spacer to move the bulb back a bit in the reflector or (if you can think of a way of doing it) trimming the mount so that it's deeper into the reflector. It'd probably be best to optimise the low beam pattern and just hope that high beam turns out OK.