Yes, hours of thinking it through and then putting it to words is quite hard! Sounds like you've got a good plan in action. It is funny, the thought of trying to conserve space in such a large tank but the space goes so quickly! I ended up going with a taller tank (23 tall x 13 x 30) just to be able to have land and water in the same tank! by the time I add up 5 inches of water, a bit of air space, a layer of foam and planting substrate I now have about 15 inches of height left to play with!
Good luck - looking forward to the next round of updates!