shedbob said:
On my tail light lens the reflector element sits directly behind the bulb & was blocking most of the light.
That was something I noticed on my '73 3c with the original reflector, especially when I was trying to fit the lowest wattage bulbs I could use because of the hopelessly inadequate alternator. The reflector element in the lens blocked out most of the light from the bulb.
Problem was solved when I was washing the bike one day and the centrally mounted plastic lens element that covered the reflector just came off as I was washing it!

The reflector was just a piece of reflective paper that got wet and separated. I peeled/scraped the rest of the paper off, glued the plastic bit back in place, and now I had a lens that probably wasn't as reflective as the original but had much higher visibility 8).
I've noticed that newer CEV lenses don't seem to have the reflective paper sandwich, just moulded in 1 piece. Looks like the reflective paper idea may not have been such a good one :

.
Ken