For 2 Extremes mounted in parallel to your tank length, you'll need to mount them about 12"-15" above the tank for good coverage toward the top ends. The ReeFlectors are designed with 90deg spread. Within the 90deg spread looking up toward the light will be very bright. Otherwise, with the LED recessed in the ReeFlectors, you won't get much glare outside of the 90deg spread. Because your tank is only 18" deep, with 2 Extremes you'll need to balance how much light spill out of the front and back with side to side coverage. Maybe mount them around 10" above the water. You'll have darker area at the very top ends of the tank and a little spillage in the front. The spillage will be noticeable only if you're sitting low and looking up toward the light within the 90deg spread.
As for waiting for the Uno, latest status is the metal core PCB will be completed next week follow by LEDs and components soldering. Heatsink, vapor cooling, and fan control designs are done. I'm finalizing the plastic shell designs with thread inserts then takes 30 days to create the plastic injection molding. Then testing, assembly, more testing, and packaging.