I just read somewhere a "rule of thumb" for setting the best pressure for gas milage vs. wear vs. safety: half way between the maximum recommended cold pressure (32 PSI for Fit) and the maximum safe pressure (51 PSI as marked on tire - may be different for some tires - I think that is a number used when installing the tire on the rim.) That calculates to be 42 PSI COLD. There is also the term: "Maximum Permissible Inflation" that some manufacturers spec which is different from that 51 PSI number.
I have also heard a good test is to check cold pressure against hot (after 10 miles or so driving) if there is about a 5 PSI rise that is good. any more or less means you need to reset the cold pressure. Searching the internet on tire pressure questions is lots of fun. Everybody says under-inflation is worst! Check this site:
http://www.tirerack.com/tires/tirete....jsp?techid=73
HOWEVER - all of this is not a proven rule and if you blow a tire or anything it is not my fault!!!!!!! Follow the Honda Way ;-)
BTW, Did you read your Fit manual or stickers enough to notice that the MAXIMUM LOAD is actually 850 Lbs? That is passengers and cargo combined, total. So 5 big guys and a couple of full kegs is way too much - even if they fit!
As they say, YMMV (Your Milage May Vary...)