I was just thinking about and working on brigthening the tail lamps this weekend. Looks like you are using some sort of metallized pastic fo he reflectors.
While that's real high reflectivity, I feel it is important to also maintain the elliptic curved reflector surface as flat reflectors disperse more widely and don't concentrate the light in the direction of the traffic following you. Do you have a similar solution for top/bottom surface or did you just paint?
I installed Bare Metal Foil - the Ultra Chrome version. It's a bit more painstaking, but it conforms well to the curved surfaces and holds up well (at least it has on my car over the past 6 months).
http://www.bare-metal.com/bare-metal-foil.html
2 sheets should be plenty for both square tails with some leftover for other areas like inside the speedo/tach etc.
Another thing I found is that the commonly used recommended bulb (#97) is half the wattage of the what was originally specified. Instead #5008 R10W 6CP is 50% brighter. There are 8-10CP bulbs avail, but they also seem to be shorter life (200hrs) which may be ok for some and not for
others.
Went outside and took some pics (SLR manual mode on tripod):
First with R5W on both sides. The right tail light was covered with BMF on the concave surfaces with BMF Chrome foil about 6mos ago. The left one I had not covered then, but did so last weekend on the concave and top & bottom surfaces with Ultra Chrome foils. It is a brighter than the right even when I switch the bulbs around. Will fix the right side soon.
Now with the Eiko R10W in the right tail (which is slightly less reflective)
Without lens -- R10W in left, R5W in right.
R10w in both
My conclusions -- R10W definitely the way to go. Not covering all surfaces does seem to impact reflectivity.
Byas