as said not sure how much this matches up exactley with
how we played it in terms of tuning, ive left the verses mostly blank as i havent finished any good ideas for them.
that section after the second chorus is the bit withe held chord we did in the jam, probably needs some refinement.
this version of the structure:
A(intro), B(riff verse), C(chorus), B, C, D(held chord part),B, A(intro as outro)

so the two root notes of the verse in this case seeme to be 
A and C. 
A is augmented with G and C with Bb. 
chorus part is: G A Bb F D. 


MemoryJack