MORE OVERCALLS

Spock jumped as the Klingon warrior banged his fist on the blue plasti-form table.
"You tell me to compete; to be aggressive; to overcall with thin values; now suddenly you get all cautious and tell me NOT to overcall with this hand. What's the truth?"
Spock considered the hand under scrutiny on the integrated Bridge visi-display:
xx
Qxx
Qxxxx
AKx
"So, you were Vulnerable, they were not, RHO opened 1S, you overcalled 2D, LHO made a negative Double, both partner and RHO passed and you went for -800?"
The Klingon snarled his assent. "At least everybody else did the same with my hand - with different results, I admit."
Spock considered the hand carefully. "There are three main reasons why you should overcall. 1) To obstruct. 2) To steal. 3) To suggest a lead."
"I understand all that." said the Klingon firmly. "What I don't get is why it was so wrong this time."
"Consider first the Vulnerability. This is crucial. They were Not Vul but you were. Even 1 down doubled is -200. Overcalls at the 1 level can be made on thin values - especially when Not Vul. However the 2 level is hugely different. When you go into battle you first make sure you have the weapons and armour you need, with your phaser set to 'KILL', don't you?"
"Oh yes." murmured the Klingon.
"So why would you go into battle with this deeply useless scrappy awful little Diamond suit? You don't want partner to lead it and you neither obstruct nor steal. In fact, you stick you head up and get it blown away. Why? Because you were not enough armoured. When you overcall VULNERABLE at the 2 level you need a much better suit - AKxxxx perhaps, and/or a better hand. The hand above is barely, at the very outside, worth an opening 1NT, 3rd in hand, Not Vulnerable. On a good day...  Also to consider is the hand shape - 5332. This a NT shape. If you can't overcall in NT's (15+) then it is almost always right to pass with these hands. At whatever Vulnerability. I might - just about - allow it if the hand looked like this with high cards concentrated in the long suit..."
xx
Qxx
AKQxx
xxx
The Klingon looked thoughtful. "So. If I want to overcall at the 2 level - and we are Vulnerable - I better really, really, really mean it?"
"In the long run, to be precise, the odds favour a 6 card suit with 2 of the top 3 honours."