The project is an Aventura II which is very similar to the sea rey. Time has come to lay out my panel. The engine I am using is a Suzuki automotive conversion similar to the Honda Viking in operating principles. I was trained in a Pietenpol with an A65 engine and the operation and MO on this aircraft is obviously quite different. The knowledge that I am bringing in is very limited in this area as a result. As of now my plan is to have an Altimeter, Air speed, VSI tach, water temp, oil pressure, Fuel gauge, voltage gauge and I'm debating on oil temp and egt / cht. I have the oil temp and egt / cht gauges but I'm just not too sure if I want to install them. Unless I buy 4 cht probes, 4 egt probes and the switches for them i think the egt / cht is largely worthless and that cost will add up quick and I 'm just not sure if it really adds any value. With a water cooled engine I see oil temp as not providing a whole lot of information. This engine is obd2 and I will have a bluetooth dongle which will be connected to a dedicated phone (operating as a small instument panel) giving me additional engine diagnostics such as 02 sensor output. I see that as providing as much indication as a single egt probe would. My other big question is the power circuits. What would you typically include on circuits and what should have dedicated circuits? I'm going to have a radio, intercom, and transponder. I've had a really hard time finding information on these things. Specifically reviews. I want to go used as much as possible on these. I've seena lot of the KT76a' transponders by king for a very reasonable price. Any experience with those?