Replacing rotten flat roof

HI
I have a porch (looks diy) built on to the back of the house about 1m x 2m with a flat felt roof.
It leaked like a sieve (temporarily fixed with bitumen) and the timber is rotten so it will have to be repaired.
It is a rather dark corner of the house so I would like to replace the roof with multiwall polycarbonate sheeting to let more light in.
Is it possible to replace felt with this type of material if I build up an incline?
What is the best way to fix the sheets down can I use those "buttons" to fix onto the timber?
Bit wary of nailing holes in the sheets how do you seal it after?
Thanks
G.

The polycabonate roof is fitted to inverted 'T' profile aluminium track and then a pvc cover clip on strip makes the joint watertight.
Something like this.
http://img.en.china.cn/0/0,0,493,19501,400,267,420eb46e.jpg