private double getMidStripeSplitRatio(long smallerSize, long largerSize, long lastLargerSize) {
    return (double) (largerSize - lastLargerSize / 2f) / (smallerSize + lastLargerSize / 2f);
  }
Override of getSplitPoint that determines the split point as the boundary between two stripes,
unless it causes significant imbalance between split sides' sizes. In that case, the split
boundary will be chosen from the middle of one of the stripes to minimize imbalance.
@return The split point, or null if no split is possible.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StripeStoreFileManager.java