I would say the katam over your henna will definitely make it dark - really dark, like mine. Unless you let it sit overnight first, that might help! Try that in your strand tests.

If you want to go lighter, I'd say definitely try the honey lightening instead (I am going to go back to this myself, this color is so darn dark!). I had really a lot of success with lightening with my Mellie's Mix (see my photo albums) if you want to try that, or use ktani's latest recommendations!