Terry, I was interested in your post because I addressed the same types of questions when lighting my dining room (planning to have prints on the walls) and my computer/printing photography work area. You should look carefully at a photometrics chart. I'm looking at a 2006-2007 one from Lightolier, titled "Accent Lighting Performance Data" at the back of their "Lighting Handbook," a thick catalog for which I'm sure there is a current version. Your original estimate of one 50-watt approx. 40 degree spread MR-16 bulb per panel sounded right to me. Looking at the chart and applying your numbers, with one bulb per panel, your bulb would be 2 feet out from the panel and 3.5 feet from the center of the portion you want to light. That gives you only 63 foot candles at the center of your beam. You should figure out what an appropriate level of foot-candle illumination is for the type of display you have in mind. Interestingly, with the angle of the beam (about 30 degrees; it is measured as compared with a straight vertical drop), the chart indicates you would get a 2.9 foot spread horizontal beam 3.5 feet from the bulb, and a 9.7 foot vertical spread. Bear in mind that the beam spread measures the point at which the foot candles are only half of what they are at the center of the beam. To get the same illumination at the edges as you have at the center, you need another bulb the same distance from the original one as the beam spread. That is, if your beam spread is 2.9 feet, you need the bulbs to be 2.9 feet apart to get even illumination, and you need an extra one on each end if you're concerned about the outside areas of your display. This stuff is complicated. BTW, I would endorse your use of 3500 Kelvin bulbs. They're closer to the light temperatures people have in their homes. Even my PAR 30 halogens in recessed lighting are warmer than that. The MR-16 bulbs certainly look contemporary, but compared to bulbs with a broader light source, you end up needing more of them. BTW, I add diffusers to mine to cut down on the glare, and provide a protective shield should anything shatter., as they can do. If you want to talk with another company about the photometrics information, I would call Bulbrite. Online they are www.bulbrite.com
. It does seem that with the lighting angle you are planning, your issue is really the horizontal beam spread and footcandles that yields, rather than the vertical spread. Good luck. Let us know how it turns out.