Do you mean replacing or moving the pot with some wires? Would it have to do with the wire length, or was it the remote pot itself? I was assuming a mechanical connection to the original part.
Or do you mean instability in general when trying to adjust during operation? I had a similar problem in my COB floodlight(still not quite finished but prototype stage published) build occurring even at about 50-70 watts, but then again I was running at more than 100% voltage boost and the converter was a smaller underpowered one. It's probably not bad at all(the version that has two trim pots, most have only one), but it's just too small. The one I have now(identical to what OL is using) seems stable at least up to 100 watts even when stepping up from 12 volts.
Is there any way to add a block with some fins? On my build, even a small fan makes a huge difference. I'm cheating by using a CPU heatpipe tower cooler, but I think any finned solid heatsink part would help quite a bit. Of course your build has a huge heat capacity, so thermal-wise it will tolerate short runtimes at almost any output. Given the huge amount of metal everywhere, fins might also help even if not directly mounted on the... ... pill.
That's what I was assuming. Probably I'm just being paranoid. That professional grade array should be strong enough to take a lot of any possible momentary overload during power up.
Hey! I'm sure the generic "100 watt" China COB with 11k chinalumens will reach at least 5001 lumens when slightly overdriven! 