Replacing rotten flat roof

[OhGranny]

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.

 

[foxhole]

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