Found a bit of a fix.. I set a Tasker profile with an application context with Car Panel that sets GPS off. It does the trick, and if I tap the maps button, GPS pops back on automatically, and turns back off when switched back to Car panel.
but if I tap navigation, I get a dialog box saying "GPS is disabled. Show location settings?" with an OK. GPS is enabled by the time this dialog box comes up, but no matter what it kicks me back out to Car Panel.. any thoughts on this; is there a way to force it to ignore that GPS is disabled for the few milliseconds it takes for Tasker to re-enable it?