As has been mentioned, you'll want to be around 6' high. The ideal range is somewhere between 6' and 6'8". Here's a photo of my standard Autana with the adjustable rack set at 6'. You can see there is a little bit of slack in the walls of the annex at 6' but still very acceptable.
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The rack on my Cruiser is at 6'10" so just beyond the ideal height. I use one of the optional annex extensions available from Tepui that adds another 12" of annex height if you end up with the tent being taller. Here's how the annex fits on my cruiser WITHOUT the extension or floor attached. You can see it is just short of the ground. The floor is shaped like a dish and has a bit of a "wall" to it so it would probably work fine without the extension, but I already had one so I have been using it.