Hey Michael I just wanted to chime in. I am in no way a professional and your setup is great. My question is instead of trying to combat the sun can you maybe embrace it and shoot available light. Perhaps let the sun hit the model from the right side and use one of your mono lights with a warming filter as a fill light from the left. You could still shoot at f2.8 just up your shutter speed to maybe 1/250th(which I believe is the max sync speed of most flashs) and that should give you a nice exposure. This would both balance the light hitting the model and solve the problem of trying to combat the sun. But, like I said I am no professional I just try to throw ideas out that might be helpful.