How to maximies your time on the punching bag

[erezb]

Hey all. I have a busy semester and some classes fall on my regular boxing classes. I have a key to the boxing gym, and i go there on my own for regular work outs on times were there is no boxing class. My goal is to stay fit, but i would also want to keep those muscles that work hard in boxing well conditioned so when i do come to class, like once or twice a week i would at least stay fit enough. I figured the best way doing that is working the punching bags (heavy, double end (mexican), small pear shape etc.) I do either 6 rounds of 3 minutes or 9 rounds of 2.5 minutes with 50 sec rest. After that i lift weights, usually its divided to back, chest and legs days. I know i need to improve my cardio, and i started adding some jugging on days i finish school too late to do anything substantial.
My question/request: Can anyone recommend some boxing specific stuff i should add? (when i work with a friend we box..) How do i upgrade my punching bag workout? How many rounds do you think is enough? Is it better to do more and longer rounds with low intensity or should i keep it as intense as possible and do less rounds? I also started doing the grappler circuit again after a period that i neglected it, and it is the **** IMO. I do it on legs shoulders day.
Thanx for you info in advance. Erez.

[erezb]

I found a nice article on how to Intensify your bag work. It sounds good.
http://www.bodybuilding.com/fun/rossboxing3.htm