So why not run them in series at a higher voltage (to compesate for the forward voltage of 4 diodes). This will keep the current the same, easier to drive and modulate (although I dont know if the flexmod can boost the voltage that high). That, and it is generally better then parraleling diodes off one source, each diode's Vfwd will differ a little bit and will cause others to run at different powers, or one diode will hog the power and overload itself.
(Ive had that happen in the case of LEDs and rectifier diodes, where the diode with the lowest forward voltage in a parralel bank drew most of the current, and promptly fried itself (raw diode array, no limiting of any kind aside from the power source).
Maybe I am missing something about this build, but generally running diodes (any diode) in parralel from the same source without any ballancing/individual limiting is a bad idea. A series bank eliminates most of these issues, as your bank behaves more or less like one diode with the combined Vfwd of all the diodes used.
EDIT : Bah, NVM, for some reason not all the pictures loaded for me and I see he is using some resistors there for each diode, this is okay too
Andy, I know lots of people ask you what knife-edging is. Well, I was wondering, what exactly is kn--- just kidding. Just wanted to comment that your last picture is probably the best pictorial representation of knife-edging.