youve got a lot of ideas to cover, my opinions on some issues are
1. framed solid roof is HEAVY but desirable as its less prone to wind, structure needs to be solid enough to support it
2. Wall height - high enough to walk into when closed ( just)
3. scope height- this is a balance between protection from wind and horizon level ( if its too low , limited chance for low objects, if high then wind can effect, bassnuts ideas have merit for auto use. i have mine so when at its LOWEST possible, the roof can just close.
4. thermal stability- mine is all timber with exception of roofing iron.
5. 3x3 is adequate for most uses, i get scope plus table in comfortably.
6. SCP is always visible well above wall height.
7. height of floor- to clear obstacles next door why not lift it and have a chipboard floor- just paint it to stop it from rotting.
http://stormfrontobservatory.googlep...ryconstruction this is how i did mine, might give you an idea or two .... maybee not
good luck with your project
cheers clive.