Dave,
Basically, mount the lamps as close to each other as possible (If
U-shaped, overlap them in layers). When looking at the lamps (when off,
of course), there should be seen a continuous area of lamps.
In general, the further away from the lamps the better the uniformity.
However, printing time will also increase. Find what works best. NOTE:
do not use reflectors as they will hinder uniformity. A matt white lamp
enclosure works best.
The wattage of a lamp is not relevant by itself. The size of the lamp
must also be known. Since most lamps are much longer than they are
wide, the length may be used. The amount of light will be greater (thus
the less printing time) from a larger ratio of wattage per length. For
example a 2 foot 20 watt lamp will print faster than a 5 foot 40 watt
lamp. Of course different lamp spectrums can influence printing time as
well.
Hope this has been helpful.
Jeff