Help Sort me out Adding alumium Roof tomororw!

I will be adding the roof to my teardrop tomorrow (July 6th 2017) I was planing to do a total contact cement job but now I'm realizing floating it might be easier.
Please double check my methodology to confirm I'm on the right track.
Place the 0.040 aluminum over the frame. In my case i have a single 8.5' wide by 13' 5.5" piece to work with. (trailer is ~6' wide and the outer edge is 13' 6" )
I will attach the aluminum to the front bottom of the trailer and work my way to the back making sure the aluminum is pulled tight. adding screws along the edge (about every 6" or so) and with the countersunk screw heads pulled in flush.
Once all the screws are in i can flush trim the excess with a router. I can remove the screws holding down the aluminum and attach the trim with screws through the trim, aluminum and butyl tape going from the aluminum face to the underside of the trim. The back edge will end slightly short of the bottom of the trailer and i will cover that area with a piece of custom wood trim. i will also add some custom wood trim to the bottom front edge.
the alternative to this is to cut the aluminum just slightly undersized to the top of the trailer and avoid the router trimming aspect.
I have ordered the roofing aluminum and the trim B following the link below.
http://rvsiding.com/aluminum/
This Forum has so much great info, i wish i found it sooner, i will put up pictures of my build but im just rushing like crazy to get everything ready to go this Friday!
Please double check my methodology to confirm I'm on the right track.
Place the 0.040 aluminum over the frame. In my case i have a single 8.5' wide by 13' 5.5" piece to work with. (trailer is ~6' wide and the outer edge is 13' 6" )
I will attach the aluminum to the front bottom of the trailer and work my way to the back making sure the aluminum is pulled tight. adding screws along the edge (about every 6" or so) and with the countersunk screw heads pulled in flush.
Once all the screws are in i can flush trim the excess with a router. I can remove the screws holding down the aluminum and attach the trim with screws through the trim, aluminum and butyl tape going from the aluminum face to the underside of the trim. The back edge will end slightly short of the bottom of the trailer and i will cover that area with a piece of custom wood trim. i will also add some custom wood trim to the bottom front edge.
the alternative to this is to cut the aluminum just slightly undersized to the top of the trailer and avoid the router trimming aspect.
I have ordered the roofing aluminum and the trim B following the link below.
http://rvsiding.com/aluminum/
This Forum has so much great info, i wish i found it sooner, i will put up pictures of my build but im just rushing like crazy to get everything ready to go this Friday!