[ QUOTE ]
Kwaz, this is a very well thought-out reply, and I understand what you're saying. I have three issues:

1. I think you are significantly over-estimating the likelihood that players are going to bow out on any street (but especially the flop) when they've already put money in.

[/ QUOTE ]

This I can see as a strong arguement. But if you are villian facing 2 back to you without a flush or str8 draw, what do YOU do?
For every one person you knock out who would have given one extra bet, you cost yourself .54sb.
If SB would have called 2 but not 3, you've just blown away all your profit from making this play.

[ QUOTE ]

2. When either the flush or straight card falls on the turn, it's likely to kill your action. Even if the donks with overcards that were going crazy on the flop don't recognize the flush/straight, they're still less likely to still be crazy on the big-bet street with UI overcards. It may only be 1BB difference, but where do you plan to make up that 1BB?

[/ QUOTE ]
I make it up when it DOESN'T kill my action. That's the point. Both 1 and 2 seem contradictory. If they're dumb enough to cold call the flop, how are they smart enough not to bet the turn when my card comes. If they are smart enough to not bet the turn, it's only because I let them know what I had (or scared them)by 3 betting the flop.
[ QUOTE ]

3. Again, maybe it's only a 1BB swing, but if a hand like this comes up once every 50 hands, that's 2BB/100 added to your winrate if you get it in...actually, it's only 1BB/100 because it costs you an extra .5BB when you lose and you only add 1BB when you win. But, you see my point.

[/ QUOTE ]

When you make your hand and the aggressor bets out on the turn, you stand to make an extra ~85% of a possible 8BB. You can see how infrequently this line has to be correct to be more profitable.

Dont get me wrong. I'm all in favour of pushing massive edges when you've got them. And like I said I'm all in favour of 3 betting the str8 flush draw. I just think that in this case it is wrong. So if the str8\flush situation comes up 1:50 hands, then this particular str8/flush situation comes up maybe 1:400 hands.

The criteria has to be.
- I've got the underside of the str8\flush and I'm not clearing up outs by 3betting.
- I'm facing more than 1 villian with 2 cold when I 3 bet.
- There are two aggressors in the hand and I have relative position on the major aggressor for the following rounds.