Joy,
Do you anticipate a larger trailer down the road? If so, as mentioned seriously consider going 40'. If not, I would still go with the 36' like it sounds you will. 10' legs for the added clearance. Last thing you want is to not get the tt exactly where it needs to be and possibly hit the a/c.
As for siding vs no siding, what about no siding for now, but ask if the clear lexan (think that's what most are made from) panels that are often used as a deck roof can be used. That way you still get some light, but are protecting the tt a little more. Panels are available in clear or smoked.