A std bore-scope will allow you to look inside for 24" or 26".  Ref. harbor
freight for a relatively cheep one (~$200'ish).
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94958

I also had some success with buying a small pc/USB camera (~$35), extracting
it from it's plastic housing, and taping it to the end of a coat hanger.
After dropping a small flashlight into the fuel cavity from the filler(with
a string), I was able to "look around" in that cavity and the next one
(through the rib holes).  I was also able to look in through the fuel gauge
hole in the root.  I had some sample shots, but can't locate them.

Rick