I am not sure if this is true, the man who sold this flash showed me a shot using E-20 with a metz flashgun, the type for wedding, and a shot with FL-40. He said that no matter what flash we buy, as long as they are not designed for digital camera, they will soft corners even if it is just slightly visible. I could not believe my eyes.
like mpenza said, maybe the flash was too zoomed in....
or maybe use a diffuser / wide angle diffuser to to ensure coverage.... or use a bounce card....
if all else fails, then buy the FL40 loh.... maybe the communication thru the TTL with FL40 will be perfectly matching.... so you don't have to worry about metering and shoot totally in "P" mode