Well, while your guess is as good as mine, the inner is 1.5m and the outer is 1.6m, but the ridge pole extends beyond the inner and curves down to the top of the door so I reckoned that at the highest point the door would be between 1.4 and 1.5m.
I haven't got the SL5 pitched at the moment, but given the door seems to come about 3/4 of the way up a 1.8m tall tent, I reckoned the door heights would be similar.
Have you found this thread on the SL5?
http://forums.bowsite.com/TF/bgforums/thread.cfm?threadid=381173&messages=22&forum=2
This gives a link to:
http://www.24hourcampfire.com/ubbthreads/ubbthreads.php/topics/3369836/1
Not all on the SL5 but some useful information. espcially on using a wood burning stove with the SL5.
The SL3s are incredibly well thought of in the backpacking community as roomy (one person tents) but big enough to get five people in for a cuppa.
I have only had the SL5 for a week so only pitched in the garden.
Its worth saying that I currently have a Hilleberg Nallo (from my proper backpacking days) and a Nomad Masai (our car tent) which replaced a Mad Bear 4.5m tipi.
I plan to replace the Nomad with an OzTent one day, but was looking for a tent to replace the Nallo that a) would erect in less than 5 minutes by one person for one night away car camping, and b) would be light enough to let us backpack it into a hill loch or maybe along sections of a Long Distance walk.
As we are getting older the prospect of crawling in and out of the Nallo is no longer very attractive and we wanted a tent that we could "live in" rather than one that you just slept in between days of walking. Good midge protection was high up on the list of desired features, and lightness was also important.
Height and space in the SL5, for lightweight tent, is great for two. The height gives a great sense of space.
Like all tipi designs the steep walls means that the usable floor space is much smaller than the measurements suggest, and for two people I wouldn't go any smaller than the SL5. The small bell end is useful for storage, but the steep sides means the outer is always pretty close, so I wouldn't like to light my Primus in the bell.
However, its easy to unclip the nest and roll it back to give you a massive area of temporary bare ground to cook on or indeed deal with getting wet jackets off. You can also do the same trick to give you a shaded seating area.
You can also unpeg the front panels and pull them out of the way to give a really good view out of the tent while still sat inside the nest. Very important if you have one of those warm sunny (but calm) Scottish evenings where midgies keep you locked in the tent.
The nest can be pitched on its own, and we plan to use it like this in for longer camps in Scotland where we will primarily be using the Nomad, but can take advantage of the midge proofed airy nest to sit in.
The outer can easily be used on its own to give a roomy but light (1.33kg) tarp/tent. It is also a very small bundle like this.The nest is a lot bulkier and heavier than the outer.
The loop to hang the outer from tree and the two side guy loops give convenient points to clip a tarp to, and this can extend over the door to give a good area of protection as well as stopping rain getting into the tent when opening the door (see below)
So all told I am pleased with my garden trials of it.
However, as with all tipi styles when you open the door you expose the inner tent area to rain, and this is something you need to learn to live with. Without a floor/nest this isn't a problem but with a floor it means it gets wet (but see above on adding a tarp)
What you shouldn't have to live with is that the hood for the air vents is too small, only just covering the vent, and rain blew through the vent, onto the nest and dripped through the mesh and puddled slightly on the groundsheet.
If this turns out to be more than a "one off" I intend adding a bit of material to either extend the hood or reduce the size of the vent. I am not at all impressed with this, especially as this was a complaint made about the older models and was meant to have been improved.
Getting the tent pitched is quick and easy. I have left the nest connected to the outer and 4 pegs plus inserting the pole gets the tent plus nest pitched.
Getting it pitched "properly" however is a bit of a fiddle, ie nylon taught all the way round, groundsheet without any folds and an equal space all the way round between inner and outer, is a faff. I am hoping I improve, and to be fair I a have only pitched it twice.
The sleeves and pole arrangement of the Exped, while probably taking a bit longer to pitch will need less fiddling to get properly pitched than the SL5 does.
I still yearn for the Venus as I thought it looked a brilliant tent, but so far I think the SL5 better fits what I wanted from this particular tent purchase.
Hope some of that is of interest, and get back to me with specific questions.
Good luck,
Graham