I would say do a full 4 wk rotation during that 6 week chunk, and another full 4wk rotation during your 4 wk chunk. A general rule is not to rock the boat as much as possible. Koval from NYU will say that this process is one of elimination versus one of acceptance, and your goal is not to give them any excuse to eliminate you. So stick to convention as much as possible. You can arrange some 2 week stint at a program with the extra time, giving you the opportunity to meet the attendings and see the program. But I'd do as many full, normal rotations as possible. Good luck.

2 week rotations seem to be the trend at smaller programs, so you could look into some of those those. but if you really want to impress i would do the whole month.
good luck