I have the MXL 670 with color head. Not sure of the differences between the 2 enlargers but you can use a color head for contrast control. My negatives are very consistent. I found it easy to just dial in magenta to increase contrast. My normal filtration is between 2 1/2 and 3 1/2, a rather narrow range. The exposure times will change slightly (under 10%). To balance exposure time between contrast grades dial in yellow with magenta in different ratios per the photo paper directions. This adds density and increases the exposure time which you may not like. Remove the red filter from the under the lens red filter assemble. Just place flat contrast filters where the red filter was.