Ground cover density is low even with multiple instances

I had a single groundcover object located at origin with a distance sufficient to cover the zone (4km x 4km). Even with the count very high, I was getting low density. As an experiment I dropped the radius to 500 and density got much better as expected.

Problem I'm having now is I changed the mission to have 16 groundcover objects evenly spaced on a 512m grid and density was very bad (a few clusters here and there) plus there was a huge framerate hit.

Here's one of my current object definitions. With 16 of these I should be seeing 16 x 20,000 grasses, but I don't think it's even 10% of that.

In TGE/A I used fxFoliageReplicator, so I'm new to using the groundcover system. Am I doing something wrong?

new GroundCover() {
      Material = "matgrass1";
      radius = "362";
      dissolveRadius = "50";
      reflectScale = "0.25";
      gridSize = "7";
      zOffset = "0";
      seed = "1";
      maxElements = "20000";
      maxBillboardTiltAngle = "90";
      shapeCullRadius = "75";
      shapesCastShadows = "1";
      billboardUVs[0] = "0 0 1 1";
      billboardUVs[1] = "0 0 1 1";
      billboardUVs[2] = "0 0 1 1";
      billboardUVs[3] = "0 0 1 1";
      billboardUVs[4] = "0 0 1 1";
      billboardUVs[5] = "0 0 1 1";
      billboardUVs[6] = "0 0 1 1";
      billboardUVs[7] = "0 0 1 1";
      invertLayer[0] = "0";
      invertLayer[1] = "0";
      invertLayer[2] = "0";
      invertLayer[3] = "0";
      invertLayer[4] = "0";
      invertLayer[5] = "0";
      invertLayer[6] = "0";
      invertLayer[7] = "0";
      probability[0] = "1";
      probability[1] = "0";
      probability[2] = "0";
      probability[3] = "0";
      probability[4] = "0";
      probability[5] = "0";
      probability[6] = "0";
      probability[7] = "0";
      sizeMin[0] = "1";
      sizeMin[1] = "1";
      sizeMin[2] = "1";
      sizeMin[3] = "1";
      sizeMin[4] = "1";
      sizeMin[5] = "1";
      sizeMin[6] = "1";
      sizeMin[7] = "1";
      sizeMax[0] = "1";
      sizeMax[1] = "1";
      sizeMax[2] = "1";
      sizeMax[3] = "1";
      sizeMax[4] = "1";
      sizeMax[5] = "1";
      sizeMax[6] = "1";
      sizeMax[7] = "1";
      sizeExponent[0] = "1";
      sizeExponent[1] = "1";
      sizeExponent[2] = "1";
      sizeExponent[3] = "1";
      sizeExponent[4] = "1";
      sizeExponent[5] = "1";
      sizeExponent[6] = "1";
      sizeExponent[7] = "1";
      windScale[0] = "1";
      windScale[1] = "1";
      windScale[2] = "1";
      windScale[3] = "1";
      windScale[4] = "1";
      windScale[5] = "1";
      windScale[6] = "1";
      windScale[7] = "1";
      minSlope[0] = "10";
      minSlope[1] = "0";
      minSlope[2] = "0";
      minSlope[3] = "0";
      minSlope[4] = "0";
      minSlope[5] = "0";
      minSlope[6] = "0";
      minSlope[7] = "0";
      maxSlope[0] = "20";
      maxSlope[1] = "0";
      maxSlope[2] = "0";
      maxSlope[3] = "0";
      maxSlope[4] = "0";
      maxSlope[5] = "0";
      maxSlope[6] = "0";
      maxSlope[7] = "0";
      minElevation[0] = "-99999";
      minElevation[1] = "-99999";
      minElevation[2] = "-99999";
      minElevation[3] = "-99999";
      minElevation[4] = "-99999";
      minElevation[5] = "-99999";
      minElevation[6] = "-99999";
      minElevation[7] = "-99999";
      maxElevation[0] = "99999";
      maxElevation[1] = "99999";
      maxElevation[2] = "99999";
      maxElevation[3] = "99999";
      maxElevation[4] = "99999";
      maxElevation[5] = "99999";
      maxElevation[6] = "99999";
      maxElevation[7] = "99999";
      minClumpCount[0] = "5";
      minClumpCount[1] = "1";
      minClumpCount[2] = "1";
      minClumpCount[3] = "1";
      minClumpCount[4] = "1";
      minClumpCount[5] = "1";
      minClumpCount[6] = "1";
      minClumpCount[7] = "1";
      maxClumpCount[0] = "10";
      maxClumpCount[1] = "1";
      maxClumpCount[2] = "1";
      maxClumpCount[3] = "1";
      maxClumpCount[4] = "1";
      maxClumpCount[5] = "1";
      maxClumpCount[6] = "1";
      maxClumpCount[7] = "1";
      clumpExponent[0] = "1";
      clumpExponent[1] = "1";
      clumpExponent[2] = "1";
      clumpExponent[3] = "1";
      clumpExponent[4] = "1";
      clumpExponent[5] = "1";
      clumpExponent[6] = "1";
      clumpExponent[7] = "1";
      clumpRadius[0] = "4";
      clumpRadius[1] = "1";
      clumpRadius[2] = "1";
      clumpRadius[3] = "1";
      clumpRadius[4] = "1";
      clumpRadius[5] = "1";
      clumpRadius[6] = "1";
      clumpRadius[7] = "1";
      windDirection = "1 0";
      windGustLength = "20";
      windGustFrequency = "4";
      windGustStrength = "0.5";
      windTurbulenceFrequency = "0.5";
      windTurbulenceStrength = "0.125";
      lockFrustum = "0";
      renderCells = "0";
      noBillboards = "0";
      noShapes = "0";
      position = "256 -256 0";
      rotation = "1 0 0 0";
      scale = "1 1 1";
      canSave = "1";
      canSaveDynamicFields = "1";
   };