D
yes cutting the shoes to go between the pins indeed acts like they are theoretically heavier but actually its a mechanical advantage as opposed to a centrifical one. I have also used a full clutch shoe cut in three pieces through the holes with the bottom of the holes trimmed for flyweights. This is an Art Carbonell thing and it works very good. have not tried it on a 710 yet but plan to.
Mugen spring: have no issue using the mugen springs. no bind.
Earlier posts about softer springs and my liking. MTX3 with stock grey shoe. with the red shoe I had to step up to the medium or hard depending on the track. Hard spring on a tight track and medium on a big track where you carry more speed through the corner. We all learn new stuff every day.