[MinaciousGrace]

afaik 5.1 doesn't specifically have any optimization for song load

There are changes that slow down load time in the custom build so that chart key generation is frontloaded rather than done during song select, however these should be negligible. My load times are ~3 seconds for 5.1 versus ~7 for 5.0.12 custom.

If your differential is that great you probably forgot to re-enable fast load or fast load for additional songs.

that being said the code that was added isn't efficient by any means and I do plan to clean it up as well as make optimizations to song load times in other capacities