All my experiences with that type of product have been dire. I have had corrugated GRP stable roofs and they havent lasted more than a few years before needing repair. Either they get a build up of crud and go opaque or the crows peck holes in them even with a fair slope on the roof. I have also tried butyl sheet but again it may be OK for a new build but once the roof gets old, wrinkled or any water ingress in the winter it is hopeless and you have to strip the roof off and start again. A good slope and sheets of corrugated iron on top of sterling OSB boards is best for shed and stables.
iPhone X review