I don't have accuturn on my 4430 but I do have a Pro 700 in it for rate and guidance.  I'm running a 372 on RTX.  I use the "offline distance" and start my turn at about 230 inches and usually get very close to my line.  My issue is that my machine wants to hang 6-8 inches offline for a 100 or so feet before totally locking on.  Last week I went into the setting and jacked everything up to max and it seems to have helped.  I also did a dead zone calibration after I'd been running for about 4 hours.  My machine will hold its line at 15 mph.