ਗ () is an interesting one.
The logical reason for the kannaa being only half the height of the letters is so that you can tell whethere you have a gaggaa or a rarraa followed by a kannaa. However, when you are writing quickly, there isn't always the opportunity to make sure that the kannaa is only half the height.
When you want to write a gaggaa, you want to make it different. You can do this by linking the left and right hand parts of the gaggaa or by writing a line over the top. Both are done here like so... .
Just be careful to make sure that whatever you do, you are consistent and unambiguous.