What are we going to change? The first change is to eliminate Weak Jump Overcalls at the two level. From now on, a jump to the two level will show an intermediate value hand. That's 12+ HCP or more, and is often only a five card suit.
Double jumps are still preemptive. Sometimes you may overcall by jumping to the three level with only a six card suit.
The second change is that all overcalls at the one level have a maximum of 12 HCP, and do not have to be five card suits. Also, they are not particularly lead directing if partner has a very good lead of her own.
If the maximum point count for a one level overcall is 12 HCP, is there a minimum? Sure, but it depends on whether or not partner is a passed hand or not.
- If partner has not yet passed, the overcall range is 8-12 HCP.
- After partner has passed, the range drops to zero! 0-12 HCP.
An important point to remember: If you are a passed hand, partner's overcall bid may have no points! Your partner is bidding both her hand and yours.
Do not raise your partner's one level overcall if you are a passed hand just because you have 8-10 points!
With extra length in partner's suit and shortness in the opponent's, go ahead.)
What about four card suits?
Yes, and often! But only at the one level.
What about three card suits?
Only if your partner is a passed hand. In this case you are trying to suggest a lead if partner doesn't have a good one. Don't be concerned about partner raising you with only three, as your agreement is that she can only raise with length in your suit and shortness in the opponent's suit. Some of your best results will come from playing in 4-3 fits at low levels, so don't be afraid to bid them. If you don't bid a three card suit, don't expect your partner to come back into the auction after passing initially with only a four card suit.
If you decide to try this, make sure your passed partner knows to never, never raise with less than 4-card support. Also, just to be ethical about this, you should announce a Pre-Alert when you sit down to play... Something like, "We make very light overcalls and bids in 3rd and 4th seat, and sometimes bid with a 3-card suit."
This may seem like a radical departure from bridge as the world knows it, but from my own experience I can tell you it works. Zero point hands and 3-card suits are not something the rest of the world is comfortable with, and because they have no experience with them, they can almost never double you at the one level for penalty. Besides, isn't bridge supposed to be fun?
And ponder this... In standard bidding the norm is that when you open a major suit you have five and partner is expected to support with three. Why can't you overcall with three and expect partner not to support unless she has five? (Or four and shortness somewhere.) Why can't you reverse those bids?
Um, did I say zero points somewhere above? Yep. Consider: Your partner passes and the next hand opens a minor. You hold this hand --
T 9 8 7 5 4 2
6 5 
8 5 3 2
and hope they play you for any missing points.
If you get doubled and get a bad result, I will personally give you a $20.00 bill. It ain't gonna happen!