Using reflectors for large group portraits (12-15 people)

[Ken Fong]

So I was using a 60" umbrella reflector for a group portrait...this size is recommended for a group of 3-4 people, but it seemed to work okay for about a dozen people (I know, I was pushing it.) A 45" was used for the fill. Ocassionaly, I had some problems with head shadows falling on the folks in the back row.
- Other than getting the people in the back to lean forward, is the other solution to get a larger reflector or move the reflectors in closer towards the camera?
- What is the downside of moving the reflectors closer to the camera...less 'depth' (fuller faces)?
- Is there a limit to how large a reflector can be for a 550EX strobe?

thanks,
Ken