Right now we have a g500 with a vacuum standby ai and a century 41. I've been watching comments from people upgrading to the gfc500 autopilot with interest for awhile as you never know when the c41 might give up the ghost. Somewhere I saw a comment I didn't understand that said there were advantages in using the g5 vs gi275 to drive the autopilot. Like the 275 wouldn't interface with the g500 or something weird. Since everything is named 5 or 500 searching is useless..  Did anyone else