Our club is going to upgrade our 172 initially with a G5 (in the HSI version) and a GNC 355. We have an STEC 30 with altitude hold installed already. I know the G5 has a built in GPSS. Is that all that's needed for the 355 and STEC to work with each other since there is a GPSS, or do you still need the Garmin GAD 29B to make them work together? I have seen on this forum some posts quoted from Garmin about the GAD 29B, but didn't know if you still needed that with the G5 installed. Or what is needed for this setup for the STEC 30, G5, and 355 to play together? Thanks for clearing this up.