Yes, it's unnecessary to size up more than it needs to be 
But it's not always you feel up to investigating everything in detail either if it's a simpler construction.
It will go great to saw up into small parts as you planned, but it's a lot more work.
But it's not always you feel up to investigating everything in detail either if it's a simpler construction.It will go great to saw up into small parts as you planned, but it's a lot more work.
I have quite a long personal experience with different types of "roof plastic". Many have a terribly short lifespan. Fiberglass-reinforced ones hold up well, but become terribly ugly over time. Polycarbonate used in multiwall sheets also holds up well.