So you have that PCB stacked with a PCB that has footprints for the LDDs on it? Did you try to get it all on to one PCB?
I started designing a version of the reefcentral LM3409 driver to plug directly into a stock Typhon, if your experiments to parallel the LDDs doesn't work out longterm that might be an interesting route to go for people who need more than 1A.
I'm tempted to put it all on one PcB, but I fear putting all my "electronic eggs into one basket" LOL I did that once by combining a Full featured Arduino w/ RTC and 6 CAT4101's onto the same PcB. Problems arose quickly after building 10 of them and passing them out among members here on this Forum. Some members had incidents with theirs that resulted in a lot of "smoked" PcB's. I want to avoid that situation, this time around, so two separate PcB's should reduce replacement costs, if damage occurs.
The "Typhon" Pcb and the LDD Pcb are separated by .5" brass standoffs. The PWM signals are passed between the boards using a 4 position .1" arduino style pin header. A common ground is shared between the Pcb's by taking advantage of the brass standoff's conductive properties.
I love the LM3409. I actually designed this version of the "Typhon" to work with an LM3409 sub PcB prior to the MeanWell LDD's. I made a dual driver version that is stackable, so that 4 LM3409's can be controlled by a single "Typhon" The LM3409's were configured to output up to 3,000ma and featured analog current control using a 250K ohm pot on the IAdj pin. Here's a photo of the LM3409 sub Pcb. (The PcB was designed to be cut into two halves)