You know the old saying, no replacement for displacement. I think a 300 would be a downgrade from your 500 since you already have modern ergos with the AF. If you are looking for a more nimble feel maybe the answer lies in the a new back half of your bike. The new narrow rail Yeti might be up your alley.
Ya you’re 100% on that. It’s never going to be a 500. They are just an absolute hoot to ride though. Like jumping on a 125 after riding a 450 on dirt. Ya you’re not going quite as fast but it’s way more fun.
Narrow rail might be an answer. But narrow track seems like a bust to me. They just don’t chew near as good.