Kit
Map shift is not really going to be an issue on a typical GA IFR GPS installation. GA GPS systems do not attempt to blend GPS data with other data (such as VOR/DME) to establish position, therefore there will be no sudden shift in position. If GPS integrity is lost, the display will be flagged (or 3D nav will degrade to 2D) and/or a RAIM warning will show for the approach.
What did you have in mind, in the GA context?
2D