I would not suggest removing all of the existing bars styles as that leaves you very little to work from.

Each bar style relates to a specific property of a group of tasks (summary, milestone, critical, manually scheduled, etc.). You can use a couple of the spare Flag fields (Flag1, Flag2, etc) for your needs. For example, use Flag1 for Shipping, Flag2 for Qualifying, and Flag3 for Investigating. The default for all Flag fields is "no", change it to yes for each of the tasks corresponding to the categories.

Take the existing "Task" bar cut it and paste twice. Add "Flag1" to the "show for" to make that bar show for tasks you have tagged with Flag1=yes. Change color, size, etc as needed. Cut that bar and paste twice and make that the Flag2 bar and so on.

You can then set the Flags as you need to for the tasks. Once you have set up the tasks, you can remove the Flag fields from your view as they are only needed to set up the category when you create the task.

I hope this helps.