That's kinda what I'm doing right now:
I am running the Peak LongLife with half a bottle of Zerex Super Protector (yes, I want my radiator squeekly clean)...it has sodium siliconate and dipotassium phoshphate as some of the active ingrdeients. We'll see how it turns out, so far so good! I'll keep on eye on pH and periodically check for precipitates. Oh and this is a 2001 Mitsu Eclipse GT.