Is this what you call it when you ease the main and get a big, backwinded bubble in the forward third or so?
The other day I was in ~18mph or so and hadn't reefed, and doing that seemed to be giving me a good ride. I was concerned it was making me look like a dope, though, so I hove to and reefed before long. ;-)
No dope. It is also called a "fisherman's reef", because it's easier for a busy, shorthanded crew to sail with a soft (not flogging!) main than to reef while standing up to your hips in a pile of dead cod.
Downside is that your main is already depowered, so there's no easy way to shed additional heeling force. If the breeze is gonna stay high for a while, I believe it's worth putting in a proper reef, flattening the main, and reserving the option of a cracked mainsheet for further gusts.
Buccs (normally) don't have reefing or backstays or travelers, so undertrimming the main is the only way to keep em upright and moving.
If the bubble shows up when you don't want it to, and it doesn't go away even when you center the boom, it prolly means your slot is too tight for the windspeed and you need some twist in the jib.