I'm planning to lay some garden path and a section outside the back door with 20/40 shingle. The clay based soil has had a skim of MOT laid over it to reduce us getting muddy when walking over it the last year or so. I have compacted this by tapping with a sledge hammer and plan to lay http://www.fleximas.co.uk/civils-and-construction/weed-control/weedban-landscape-fabric-70 (i've already brought it!) directly on top and then 2" of shingle. Is this ok? The membrane tech blurb states a thicker layer of MOT on top of the soil & then the membrane / shingle. What could go wrong with my idea of not using a thick layer of type 1?