I have a 75g I've been running for one year now with three bags of Flourite as the base and topped with Soilmaster. It's a great combo! Because the Soilmaster is much lighter weight than the Flourite I've had very little of it come up to the top level. They are both a fractured clay product so I think they work very well together. SMS has very good CEC.
I STRONGLY advise against the gravel because they'll have very different appearaces, even though they may have similar size. Flourite is fractured clay with very angular, irregular edges. If your choosen gravel is more rounded in appearance; well to me, it clashes - I find it visually annoying.