A thing I learned from Shiro
"Remember this is a game, and humans are capable of errors. Timing isn't about making a perfect match for the song, but a mix of perfect match and playable. Doing what you said here would throw almost any player off, while a full 1/6 is intuitive and is what the players will play."
This was on another mapset, but in my opinion keeping the 1/3s would be the best for playability. A weird rhythm to match the sounds here would reeeally hurt the gameplay. I would even delete the 1/3 slider and just put 1/3 circles there.
http://puu.sh/lPQkm/5fe1dae8c2.jpgAlso it's barely hearable on 100% that there are more sounds, so 1/3 should be fine in my opinion