So, as I was writing before (and in other threads too), if FastFill will consider Wrap-around fragmentation, then the problem you just described shouldn't be anymore . So I continue to not understand what are these cases where FastFill (with wrap around) might make things worse...
1) Wrapping flag should be global and Fileactions should respect the setting in both evaluation and writing.
2) Wrapping ( and "dewrapping" ) decision should be based
on how wrapping would be (is) done ( what affects performance )
and not on what would be (is) wrapped ( what does not affect performance )