hello Marijn,
About the default -- I still think a lot of people might be (intentionally or unintentionally) using ratios to fill float slots, so to me defaulting to T makes sense. People who care about precision can easily set the variable to NIL.
users can certainly set it, that's why it was added... but only *AFTER* they have understood and realized the potential dangers, which may be a long time after going live and doing serious miscalculation leading to silent data "corruption"...
but as i promised, it was my last try in this. i'm on the safe side by now anyway... :)
happy hacking,