I don't like sparring them. Any advice? What i do now is reverse some defensive moves, i.e. when i duck to my lower right when facing a good right hand orthodox puncher, i now duck to the lower left with a strong left handed south paw and vice-versa for left/right hookers. Any other things?
It's very hard to jab against a southpaw and you leave yourself open. Circle to the opposite side of their power hand (their left), and do a lot of leading right punches. A leading right-pivot to the right-left hook (head or body) seems to work well on them...
Counter left hooks seem to work well indeed. So do straight rights. For the rest you circle to the opposite side, slip to the opposite side, etc. Remember he has the exact same (dis)advantages since you're mirrored.
straight right is the best weapon. circle to the left, opposite their power hand. when they try to come in behind a jab, slip and send a right down the middle.
There you go right there. For me, using straight rights works the best. Fake him with the jab and quickly go with the straight.
Or wait for his jab, slip it to the outside (your left) and throw a left hook, if you can throw the left hook while moving backwards it's even more effective he'll walk right into it. If he lunges in a left uppercut will do. It's not my favorite punch either, but it comes kinda natural when you slip to the left. Their only advantage is experience in fighting mirrored fighters. Just make sure you fight them often and southpaws will be nothing special. I still hate them though