Something else to consider, once all safety and legal implications are thought through, is to play the company's game. Everyone knows how much direct pressure dispatch is under for fuel conservation because of how close they are to management on a daily basis. The only way to consistently get more gas is to force the company to do it by accepting diverts with their planned fuel. Yes, for some, that's contrary to our goal of getting the pax to their destination with as minimal frustration as possible. However, if companies would rather skimp on fuel, then there's nothing wrong with playing a long and making your point by following their rules and requests. Diversions are far more costly than carrying more fuel. Make it cheaper to carry the extra fuel.

Again, I'm not advocating shorting yourself on safety or legality. If dispatch plans you legal at the time of the release but your gut says you may need more fuel, you can still accept the release as-is and then do what you need to airborne all the while making my points as stated above.