[Leica] holding M6 Vertically against the light ?

[nod <smackphoto@bigfoot.com>]

I have an M6, I cannot for the life of me decide which way is best to
hold it when trying to take upright shots, I often find myself in
situations where, bright lights shine directly towards me, (amateur
dramatics group) and when held vertically the central rangefinder window
looses contrast or whites out completely.

Does anyone have any suggestions as to how this can be minimized, as
when held horizontally it does not seem to be such a great problem.

thank you

nod.