Wow, sorry I never replied to your thorough answer! It's odd to me that I have to add my own posts to a watch list, I must have forgotten to do that here. Most forums seem to auto-notify for new posts and replies. (let me know if I'm missing something!)
Anyway... Vertex got back to me and said the following:
"150ft runs are more than okay for this unit, it will all depend on what the running pressure is. Typically as long as it does not exceed 500-700ft you'll be fine.
The remote valve box is a great option if the power supply is a significant distant [sic] from the pond. This would run one single line from the cabinet preferably a 1" PVC you can source locally into a remote in ground valve box at the pond where you can hook up the tubing and control the valves. This is a great alternative to paying to bring electrical closer."
So, perhaps the remote valve box would do the trick? That's what I was planning, having the two pressure "circuits" in parallel rather than in series, starting all the way back at the compressor or at the pond's edge. Alternatively, I could run weighted tubing to the midpoint between the compressors (~250ft) and then Tee out ~100ft to each diffuser station. Do you think I'd need to go to something more powerful if these diffusers are set at 10-12 ft depth?
