The best advice here is to try it. I have heard of everything topping SiO2 coatings. The main thing to remember is most toppers will not bond for any length of time over a coating. After all that is why we pay big bucks for a coating, so stuff will not stick to it. Right now I am enjoying using ECHO2 mixed with a SiO2 topper (and distilled water) as a QD as it cleans and shines in one step without marring or scratching (I also use it as a drying aid). The Sonax stuff will not hurt the coating, it just may not last very long.