Hey Rasta,
Right now I'm too sleepy to do the calculations for the lumens... But I had an idea:: I think that you should place your bulb horizontally... instead of vertically... I think, think , that the majority of 'photons' being generated from the bulb would be on the horizontal directions...

Can't you get some mylar? If you're able to, you can cover some cardboard with Mylar... then place that over your bulb/fixture.

Cowa Bunga,

turtle420