If you try it again, I think you will find it will fit in tall mode. My road bike frame is about the same size, and it fits fine. Here's what I suggest:

Remove front wheel. Open the left side rear door. Put the rear wheel end of the bike in first, with the rear wheel in the "corner" between the back of the front passenger seat and the right rear door. Now rotate the handlebars of the bike to the left and lift up the front of the bike. The brake levers should rest on the top of the raised seat bottom, giving them a nice soft cushion and holding the bike in place. You will now have plenty of room for your front wheel plus lots of other stuff! Give it a try!

 

I'm bumping this older thread now that most of you have had your Fits for awhile. I saw this pic on Honda's website and I want to know how accurate this is? I ride a 20-21" framed Mt Bike. Thanks.

 

I have yet to try it like that..
maybe somebody could email honda and see if they could tell us the size of that bike in the pic?

 

With the back seats folded down I was able to fit 2 complete bikes on top of one another.

 

With back seats down i fit 3 bmx's in,or my medium frame norco rival by itself(all intact)