Andrew,
Out of interest what tube bender did you use
and what tubing is the barwork made from
I really like you work.
And I think an Al sheet for the roof would be a great option for heat load but also much nicer to walk around on!
Just a quick opinion, if you moved the across roof bar rearward about 75mm, you would then be able to mount a light bar along the roof nicely with the Al sheet coming up to protect it from loads on the roof.
S

