Considering your stated design parameters, have you considered using conventional F15T8 bulbs? The F15T8BL or BLB bulb would expose all graded papers including Azo. The F15T8BLB bulbs are available at Walmart for about $4.00 each. There are electronic ballasts available to fire these lamps....I had thought at one time of building an 8X10 enlarger head for my Durst 138S and stacking these bulbs as near to each other as I could.