First of all we recommend you to use the same dimensions of sensors (diamond pattern size, gap between diamond pattern) as that of the Trackpad design since it is tested by us.
Based on your trackpad physical dimensions you can reduce/increase the number of rows/columns. In your case since the size of your trackpad is less than the one recommended by us, you can reduce the number of rows and columns.
Now since you are using same dimensions as that of our reference trackpad, you can reduce the values of x and y co-ordinates in the same ratio (decrease them by a 2 factor to 200).
Please implement these changes and check once, if they dont work we can help you in finding different set of tuning parameters.