Dometic CCII Control Board for Penquin II

The reason I suggested adding the remote interior temp sensor is to allow that 2nd ext unit to turn off and on, by sensing the actual temp of the area it is cooling. I also do not know what the problems may be by setting it at Zone 3, versus just an extension of Zone 1. If the 2 AC units were within 5 feet or less, than using the wall tstat may be best. I looked at a similar model Cedar Creek and it did show a middle AC, then all the way up front, the front AC and all the way at the back, the rear AC. Indeed 10 to 15 foot spacing. Is your front the LR or the Bedroom? Front to rear, which AC units are EXT? Doug