Okay, it looks like a site like this would be helpful to answer some of these questions. Hope this link copies okay, but here we go. Assuming we have accurate gear ratio data:
MFactory Competition Products - THE Replacement for Displacement!

 

Changing to a longer final drive (lower ratio number) won't just affect your 5th gear, but all 1st-5th gears. Unless you have the power available, this is going to bog your car rather seriously, especially on a FIT.

For the fuel economy aspect, changing to a shorter final drive (higher ratio number) might actually increase your mpg due to less load/throttle during normal cruising speeds. This has been shown to be the case on both D-Series and B-Series, although we've still to test on the FIT.

 

Crap! I wish I had seen this thread when people's insults were still here!
Not that that's OK, but it is entertaining sometimes.
That's the nature of the Internet.

 

If I'm not mistaken, it looks like the new 2009 MT version actually has a higher actual gear ratio (5th gear ratio x final drive ratio) than the 2008 manual:
2008 2009
3.24753 3.35874

So the 2009 would rev even higher at highway speeds? Is that right?

Frank