The SetSize parameter defines the radius of a circumferrential sphere around the vessel.
The touchdown points should stick out of this sphere. It seems Orbiter 2015 is interpreting this more stringent than previous versions.
Otherwise the ground collision detection may give error results.
These points do not really need to represent any physical landing leg, or so.
Below is what I use for the Orion-MPCV:
SetSize (6);
...
SetTouchdownPoints( _V(0,-5, -4), _V(-5, 3, -4), _V( 5, 3,-4));