I have the filter drawer Aristo cold light head using the V54 lamp (see my thread several threads below yours). I called Aristo and was told that the Dual bulb head is slower than the single bulb with filters. I am using Dupont filters trying a variety of papers, and the contrast response of different papers can be very different. I find Dupont MGIV to be the contrastiest, with a #.5 - #1 filter being near normal for me (my reference is Seagull G#2 graded). The lowest contrast paper is Seagull VC with the highest contrast I can get falling slightly short of Seagull G #4 graded. All of these papers are fiber, by the way.
Also, with the filter drawer head, I live with long exposures.