I have difficulties keeping the razor down properly on the return stroke too, when held 90 degrees across the strop. But have no trouble at all with a heel-leading diagonal stroke. I learned on a narrower strop. I can concentrate on my finger positioning and all and make a good 90 stroke, but it's a ton easier, for me, to just X it. Learn it right. I used "stop, turn, go" chanting in my head for the first few thousand strokes.
To change directions it has to stop. If turned after that stop,
never no nicks.
learn a lot about stropping here:
http://straightrazorpalace.com/strop...st-2012-a.html