in Example 4 objects around the player.
When the player was on the floor is all right. If the player is in a vehicle which objects are in front of him in the bottom countersunk, werend the objects behind him hanging in the air. Just the Right and Left are on the height of the player.
{_obj = (_x select 0) createvehicle [0,0,0];
_obj setPos ( player modelToWorld [(_x select 1) select 0,(_x select 1) select 1,0] );
_obj setDir ( (getDir player) - (_x select 2) ); } forEach [["Land_HBarrierBig_F",[-5.09961,-26,0],0],["Land_HBarrierBig_F",[-35.5996,3.10059,0],90],["Land_HBarrierBig_F",[4.90039,33,0],0], ["Land_HBarrierBig_F",[41.9004,4.2002,0],90]];
modelToWorld takes into account vectorUp of the object. While on foot player's vectorUp is [0,0,1], when in vehicle it can be different, tilted forward a bit like in your case.
player setVectorUp [0,0,1];
{_obj = (_x select 0) createvehicle [0,0,0];
_obj setPos ( player modelToWorld [(_x select 1) select 0,(_x select 1) select 1,0] );
_obj setDir ( (getDir player) - (_x select 2) ); } forEach [["Land_HBarrierBig_F",[-5.09961,-26,0],0],["Land_HBarrierBig_F",[-35.5996,3.10059,0],90],["Land_HBarrierBig_F",[4.90039,33,0],0], ["Land_HBarrierBig_F",[41.9004,4.2002,0],90]];
does the trick already, but I suggest you reference the actual vehicle
vehicle player
which should work for both on foot and in vehicle
{_obj = (_x select 0) createvehicle [0,0,0];
_obj setPos ( vehicle player modelToWorld [(_x select 1) select 0,(_x select 1) select 1,0] );
_obj setDir ( (getDir vehicle player) - (_x select 2) ); } forEach [["Land_HBarrierBig_F",[-5.09961,-26,0],0],["Land_HBarrierBig_F",[-35.5996,3.10059,0],90],["Land_HBarrierBig_F",[4.90039,33,0],0], ["Land_HBarrierBig_F",[41.9004,4.2002,0],90]];
EDIT minus vehicle height offset. 1st method is probably better.