Ah, didn't realize it was scrounged
I think it is probably pvc (much of the polycarbonate roofing on the market is square-corrugated rather than wavy-corrugated, although not *all*). Who knows what brand, but they are all about the same.
So I would suggest looking at this http://www.palramamericas.com/docs/upload/Palruf_Installation_Guide.pdf for the full specs.
(even if it is actually polycarbonate, which is the tougher of the two materials, the installation specs are pretty close to the same, so follow the Palruf sheet)
You may not THINK that excess overhang, or insufficient wood support under it, could allow it to get ripped off, but DOES, as many BYCers have experienced. All's it takes is for the wind to get under one edge with enough force to pry hard enough, and it just rips all to pieces. (Thus, you must keep the overhang to such a small amount that the wind force on it won't BE that strong a prying force).
I would suggest at least adding some spacers between the rafters, no further than 2' apart, and screwing into those every rib or two. Your overhangs are not *super way* too large, so you *could* just cross your fingers and hope, or you could pick a warm day and trim the edges back with scissors to an appropriate overhang dimension, or attach a 1x2 to the outside of your roof frame and screw thru the plastic into that every few ribs.
It would just be a shame to see all that hard work, and NICE result, get wasted in a strong gust of wind. (I'm not talking hurricane, either)
Just a thought anyhow, good luck, have fun,
Pat

So I would suggest looking at this http://www.palramamericas.com/docs/upload/Palruf_Installation_Guide.pdf for the full specs.
(even if it is actually polycarbonate, which is the tougher of the two materials, the installation specs are pretty close to the same, so follow the Palruf sheet)
You may not THINK that excess overhang, or insufficient wood support under it, could allow it to get ripped off, but DOES, as many BYCers have experienced. All's it takes is for the wind to get under one edge with enough force to pry hard enough, and it just rips all to pieces. (Thus, you must keep the overhang to such a small amount that the wind force on it won't BE that strong a prying force).
I would suggest at least adding some spacers between the rafters, no further than 2' apart, and screwing into those every rib or two. Your overhangs are not *super way* too large, so you *could* just cross your fingers and hope, or you could pick a warm day and trim the edges back with scissors to an appropriate overhang dimension, or attach a 1x2 to the outside of your roof frame and screw thru the plastic into that every few ribs.
It would just be a shame to see all that hard work, and NICE result, get wasted in a strong gust of wind. (I'm not talking hurricane, either)
Just a thought anyhow, good luck, have fun,
Pat