> -- I can tell you that putting in
>a 50-watt backup light will lead to melting/warping of the whole taillight
>assembly. :(

I have run a 50-watt halogen in the brake light socket for almost two years
with no problems.  Also have jumped the taillight circuit to the blank
socket and installed another 5-watt bulb matching the existing taillight
bulbs to enable another taillight in each housing.  More light can't be
bad.

Jeff Birk
'89 Wolfsburg with four taillight bulbs shining nicely and very bright
    brake lights