[css3-flexbox] flex() and CSS transitions

What should happen if we try to use a CSS transition between two different
flex() values?

I made a small demo in javascript that scales each value independently (pos
flex -> pos flex, neg flex -> neg flex, preferred size -> preferred size)
and it seems to behave reasonably.  I just wanted to make sure this is
something we want to support.

Also, it seems like transitioning from a fixed length to a flex() value
should just treat the fixed length as flex(0 0 [fixed length]).  Does that
seem reasonable as well?

Thanks,
Tony