No response, so I will be brief on what I have found:
1) I have not got around to troubleshooting the panel. Maybe in the spring. I believe the bulbs indicate half and full because the probes were mid and high level on the original tank.
2) Still working on and after market gauge for seeing the tank levels. There is a thread where they a building a prototype Airstream Central Control panel that will include tank levels. It is very technical....here is a link http://www.airforums.com/forums/f443...or-113265.html
3) Here art the two complete systems that people have used with good results. The sensors stick on the side of the tank so no holes in your new tank! My issue is they are spendy and I think you would need to fish the wires up to the control panel. https://www.garnetinstruments.com/rv-shop/
SensaTank II Fluid Monitoring System with Field-Effect sensors