Peaceful Lepomis?

Anyone ever have an unecpectedly peaceful Lepomis?

I have a 6 inch bluegill, who I had in a 29g holding tank, and I needed to move some smaller (1-3") sunfish in there because of a problem with another tank. I put in a tank divider made of egg crate because I figured in so small a tank he would beat the tar out of them. However, the egg crate got dislodged and I found them all together, and since they seemed fine I have just been keeping an eye them. They have been together for a week or so and they are perfectly fine so far, even in such a small tank (temporary, obviously). In fact the big[ger] bluegills prescence seems to have made the smaller sunfish stop beating each other up as much.

Do I have a fluke bluegill, or is his benevolent attitude likely to fade?

I think you may have gotten lucky, but this is not unheard of at all. I have had nasty Lepomis of various species, and some very docile ones. I think it is often luck of the draw, and something I have done right or wrong in the tank. We all make generalizations about how fish will fit in together, but there are always exceptions. Often all you can do is give it a try.

If the bluegill is female, you may never have much problem, if it is male, and goes into spawning mode????

Yes the big one may be a female, but even if it's male the small ones might not be perceived as a territorial threat.
Non-breeding bluegill are fairly gregarious, semi-schooling fish.

Or you could end up like me that has longears and the dominant male is a bully.