I flew my Maule to PeeDee Avionics in Cheraw SC (KCQW) yesterday to replace the original vacuum DG with a Garmin G5 HSI. There are many advantages to the G5 as an HSI:
No more gyroscopic precession. The G5 comes with a solid state IMU for compass data.
AI combined with HSI. You can switch the G5 to either mode. It contains an AHRS.
Primary external CDI for the GTN 650. Allows removal of the GI 106B as the CDI and lightens the aircraft slightly.
4 hr backup battery in case of electrical system outage.
Full HSI in place of DG gives much better situational awareness.
At some point I'll replace the vacuum AI with another G5, which will allow me to get rid of the entire vacuum system and lighten the aircraft by about 20 lbs. My approach to the upgrades is to do it gradually as instruments need replacement. The vacuum AI is working well and I just replaced the vacuum pump.
It will be interesting to see how easy the G5 HSI is for ILS and LPV approaches. The glide slope indicator is a vertical slide bar on the right side of the display instead of cross hairs.
I'm also having them do an IFR systems certification and GTN 650 software update, if available.
I've used PeeDee Avionics for most of my avionics upgrades. They do good quality work at a reasonable price that is below many of the other avionics shops that I've used.
I guess I should have known but I discovered that the G5 shows actual airspeed, not GPS-derived, using the pitot tube on the PFD page. A T is installed in the tubing going to your airspeed indicator and a piece of tubing goes from the T to the G5.
