nearing completion of my first 72" bingham's fiberglass longbow - the edges don't seem right to me.  
what cross section should i use?  

1.  leave it alone - resulting in sharp edges and a perfect rectangular cross section,
2.   blunt the edges, resulting in a rectangle with softer edges,
3.  really round those edges and make an oval cross section.

At the very least you should take the sharp edges off. If you don't it could lift a splinter of glass and ruin. As far as how far you go it depends on the desired draw weight you are after. Rounding the edges is the fastest way to take pounds off a bow while finishing it. It is very easy to take five pounds or so off if you get agressive with the rounding. If the bow is close to weight and you don't want to loose more weight then don't take much but make sure the sharp eges are gone like option two. Option one is not safe. Option three if the bow is a little heavier than intended.

I agree with Jason.  Mild rounding will take a pound or so.  If you get aggressive you can take several pounds off.

I sand the sharp limb edge with 150 grit sandpaper, then use 220 to finish sand the limb edges. I sand from handle to tip to avoid lifting a glass splinter, I am just rounding the fiberglass edge off like Jason said, like your #2 option.

thanks guys, now i got a cross section to shoot for. 'preciate that advice.  
hadn't even thought about splinters, i was mostly thinking about how the sharp edges are shredding my bowstrings.

That too.

I started mine by using a rat tail file down the belly and the back edges. then finished with sandpaper.

My  bows always seem to come out heavier so I needed to reduce weight also.

I really have liked the outcome as the bows are shooters.

Good Luck Mike

I like to do that too Mike. On purpose that is. When I figure a stack I will go a little heavy and then narrow or round the corners to get to weight. Mostly because I can never seem to keep all the lams perfectly lined up and keep an exact 1.5". So if I try to nail the stack for weight perfectly my bow ends up too light after I clean it up. If I go a little heavy I can narrow the bow an eigth of an inch or so and get good glue lines. I have found that I prefer a longbow that is less than 1.5" anyway. I also like to trap the belly sometimes and that takes a couple #s off too. So I will shoot for about 7 to 10 pounds over in stack then narrow 1/8" or so, profile and rough tiller picking a top limb and cut a shelf/handle. I have to remember to take the sharp edges off before I string the bow for the first time or it could lift a splinter right off the bat. Shoot it. If it feels like the tips are a little heavy I will trap the outer third belly sides. Then round the corners to bring it down to weight. That ussually eats up the extra weight. If it is really close to weight after sooting it in and final tiller I will just leave the edges slightly finish sanded round for saftey.