C.,
I have 4 boys and was told that #5 is going to be a girl. My boys are always complimented on their behavior and manners. They even received free sundaes at Cracker Barrel b/c the waitress was so impressed. Even without having a daughter yet, it is a fact that boys and girls are different. That said, your strong-willed son is even less likely to submit to positive talk and numerous time outs given this intense characteristic. Such disciplines are not "uncomfortable" enough for him to think before he repeats his actions.
Unlike many girls, his nature is not to change his behavior simply b/c you expressed your disappointment. First, I would recommend avoiding any bribes or empty threats. The truth is you expect a certain behavior b/c you expect it. You must communicate (verbally and non-verbally) that his cooperation NOT negotiable.
Second, I suggest announce to him a list of consequences that you are able and willing to implement. You must be willing to implement them even at an inconvenience to yourself (e.g. delaying an errand/task/dinner until his cooperation is complete, not attending an event, but not allowing it to become extra mommmy time for him, and leaving an event per his misbehaving.)
I give a few warnings with a consequence reminder. Then I respond according to their choice. Personally, I have found that 2, 3, or 4 smacks (not taps) on the hand (age 1-2) and on the bottom--must be felt through clothing--(age 2-4) have made the use of time out at age 5+ much more effective. The time out at an older age reinforces the expectation that the pain a few years earlier required.
All in all, if your son does not comply with you (female figure) during his 18 years in your home, imagine what kind of mate you are preparing for someone else's daughter.