Higher cons are a fact of life, and you will come up against em at some point. Your options really are:
1. Avoid them. Seriously, high cons can present a tough challenge, to which you start on your back foot. Do you best not to engage them unless your ready to fight. You don't HAVE to fly towards them and engage them. Sometimes, they jump you and you have no choice, but a lot of the time you can avoid them. To decrease your chances of being jumped by a higher con, spend some time climbing a bit yourself if you anticipate higher cons in a particular area. Give yourself some space and time to climb in peace and ensure you're able to join the hot area under more favorable conditions.
2. If you're forced to fight or you can't resist the challenge and just love reversing the tables on alt-monkeys
then what you need to do, is do everything you can to either engineer a killing snap-shot (easier to do with cannons than MGs) or attempt to even out the E disparity and then try fight a fairer fight with them or try for both.
Normally, if i spot a higher con who is keen on me, i will turn away from them and make them chase me for as much as possible. If you have alt, you can trade some of it to keep your speed high (just make sure you leave some to fight with). This will either take you to safety, or it the con will chase, in which case the will use up some E chasing you/diving on you. It also has the bonus effect of giving you some much-needed speed to maneuver more effectively with. Make them waste their E advantage.
To set up a killing snapshot, you have to get them in front of your guns, which involves either turning into them (either horizontally or vertically or combination of both) which will lead to a risky head-on shot, or force an overshoot which may present a brief snapshot opportunity, or perhaps a saddle-up chance. Even if the shot doesn't kill, its worth trying for it (espc the overshoot) as any damage can cause your opponent to panic or distract them for a moment which can be exploited.
Engineering the overshoot can be difficult and risky. you have a number of options from simple flat-scissors, a rolling scissors, or the more simple barrel-roll defense. Flat scissors is risky and wastes E, but can work if you cant fly the other moves. The easiest, and one of the safest is the barrel-roll defense. Simply put you fly a barrel-roll to compress your forward motion vector but retain speed. The key is engineering the speed differential. Too much and you wont have the snap-shot opportunity, too little and the bogey will just saddle up. My guess would be a differential of around 100 knots +- 30 sounds ok. Allow the bogey to attack from the rear quarter with the speed differential as above. At about D1.5, start a slight climbing gentle break turn to tempt the bogey into thinking they have an easy shot on you. They start to attempt to pull lead on you to get the shot. Start tightening up your break turn at around 900-1k, then at about 700-800 indicated (about when they will be pressing the fire button, don't forget net lag which adds 100-300 feet) commence your pull up and aileron roll back in the direction you broke from to enter a barrel-roll (say if you originally broke right, start your barrel-roll rolling to the left). You should now be performing a barrel-roll around the path of the bogey that is bouncing you and you should have avoided getting hit. The trick is to keep them in view as you roll (this is hard), and you have to try modify your barrel-roll so that you nose will cross the anticipated flight path of the now over-shooting bogey. When your nose gets to that point (and the bogey is yet to arrive by a split-second) squirt out some rounds and if you time it right they'll fly straight into it (and get the shock of their life).
see this film for an example:
http://www.my2cents.co.nz/AcesHigh/Films/barrellroll_defense.zip(i actaully score a hit on the overshoot, then saddle up for the kill).
Another alternative is something i call the 'high-low overshoot'. The deal here is to try trick the bogey into a steep diving attack on you - eg from directly above or close to it. Critical here is tempting them into thinking they have the shot and easy kill when they don't, and the process of their greed blow it all. You have to get them into attacking you in a steep dive while you avoid by pulling up and again doing some sort of barrel-roll to orient yourself the follow-on snap-shot. They're going down (wasting E and faster than you to start with due to their dive on you) and only make it worse by not aborting their run at you, while your going up (slowing down but building E). They have gravity increasing their turn-radius, and gravity compressing yours - perfect.
Heres one (me in a P40E) and bandit in a FW190D-9 (a MUCH faster aircraft). The 190 attacks in a steep dive and the rest is history. I score pilot wound and he musta blacked out. Still a victory is a victory.
http://www.my2cents.co.nz/AcesHigh/Films/hi-low-overshoot.zipThis one i'm attack from my high 12oc position. The text has been removed, but the 205 is killed.
http://www.my2cents.co.nz/AcesHigh/Films/HiLow_Overshoot2.zipOf course with the victories, you have to accept that you are at the disadvantage, and you will be fighting from your back foot, and a good pilot may not make mistakes you can capitalize on, and you end up dead instead.