In my testing the user had to do one of two things.
1. add the height of the rod and then subtract the arp to apc distance to the rover antenna height to get the correct elevation or
2. add the height of the rod and then subtract the arp to apc distance from the base point elevation.
I like option 2 because there is no monkeying around with the rover antenna heights. One only has to compute another point for the base and call it something like base apc height so there is no confusion of the actual point on the ground elevation. DPOS works well with this method. if option one is used then the DPOS elevations will all be off by the aforementioned height difference. One would have to change all the HRs to get correct DPOS elevations but then the rtk elevations would be wrong.
Zoltan, can you post a project where it is working correctly for you?