Roof trusses, skinning, interior ceiling, aluminum trim..


Well, I may have gotten ahead of the game but I’m building my “own” design, 5x10, so please don’t laugh when we come to NE for the annual meeting, providing we get the project done by then. The general shape of the unit is drawn an in "my gallery of photos". Well, the walls are built and I used 15/32 plywood and 1”x1/2” “nail strips” around the edges, windows, doors, etc…
Question 1: (part a) since I have a roof section of about 7’ that is flat, are 2x2’s on 7-10-12-14” centers enough or should I incorporate some steel? (part b) when attaching the “trusses” to the sides I’m not to fond of end grain screwing, do others have any ideas such as angle iron on the ends through bolted (countersunk) then through bolted through the trusses.
Question 2: exterior siding will be floating aluminum that I understand is the most favorable. Since it’s winter should I trim the aluminum a ¼” shy to give it room to expand or will flush trim be acceptable?
Question 3: for the underlayment on the roof I was going to skin w/ 1/8” plywood, glued and screwed; then contact cement a 2nd layer of 1/8” plywood, then the aluminum. I figured this would be far easier to apply and bend than one solid sheet of ¼” plywood – any thoughts, concerns?
Question 4: Interior ceiling – is bendy ply structural enough or should I stick with 1/8” smooth oak paneling? The interior sides will be 1/8” bead-board oak or birch.
Question 5: Is annealing aluminum hard to do and provide good results or should I purchase the $2 p/foot soft metal trim?
Now don’t everyone get mad all at once that a new guy is asking so many questions – I promise to make the finished product at least presentable.