George, my Rivale is very nimble. Before I bought it, I stood over a B4 and the Rivale and swung each from left to right. There was a discernible difference in the amount of mass between the two. Since then I've ridden both. The B4 (I've only ever ridden Randy's) takes noticeably more effort to drop it in to a corner compared with the Rivale. And while my F4 was telepathic through a corner, it wasn't exactly light feeling.
I'd put several hundred miles on your Stradale before you decide you need to spend $$$$ making it lighter. I think you're going to be surprised how light it feels in comparison with an F4 or B4.