In Phase I flight testing and starting to inflight tune the AP servos. Using the Dynon produced flow charts for inflight tuning. Two SV32 servos installed on STOL CH750 along with AP control panel. In simplified mode TRK/ALT along with HSI/ALT seem to hold altitude OK (smooth air). When switching to expert mode, airspeed hold seems to do quite well (smooth air). Coming out of the IAS mode into ALT hold, the autopilot will start deviating and correcting either side of the altitude until it seems to give up and drift either way from the engaged altitude. Could this be related to my ALT bug? All thoughts appreciated....thanks!