I am looking into another casting rod to become my new "All Purpose Rod". I have narrowed it down to a medium heavy action Kistler rod but I am not sure which length to choose. I am about 5' 2" in height but have handled 8 foot rods fairly well. I was looking at either the 6'9" or the 7'. Any advice appreciated.

I think for the most part rod length is a personal preference. The shortest rod i own is a 6'6" that i use for topwaters, the only reason i prefer a 6'6" over a 7' is because for me its easier to work the bait. Other than that i use 6'10" and up.

I use 6' 6" baitcasting rods when fishing two fishermen in a short boat, but otherwise I use 7 footers.  I like the way they cast, the way they handle fish, and I don't seem to have any trouble working lures the way I want.  This may be different if I were fishing from a very low fishing boat-mine is a deep V, so is higher than many bass boats.  I am 5-10.

I forgot to mention, for an all purpose rod for me I would not choose a medium heavy action.  I find medium action best for all but the heaviest of lures, and a medium heavy will not load properly with the lighter lures (1/2 oz and down), IMHO.  It will not cast as well and will not be as comfortable on the arm when used for long periods of time.

I love a medium light for crankbaits in the 1/4-3/8 weight range.

My "all-around" rod for treble hook lures is a St. Croix Avid AC66MF with a soft tip. I also use this rod for buzzbaits and spinnerbaits. The 6 1/2' length is especially comfortable when working jerkbaits and top water. My other rods are all 7'.

8-)

I forgot to mention, for an all purpose rod for me I would not choose a medium heavy action. I find medium action best for all but the heaviest of lures, and a medium heavy will not load properly with the lighter lures (1/2 oz and down), IMHO.

I don't know about that. If I were to get all purpose rod it would be a 7' medium heavy. All my MH rods cast lighter lures (1/4 oz) just fine. I think a MH has a much wider range of applications than a medium does. The only case where I would get a medium as an all purpose would be if it was a spinning rod where lighter lures are used.

IMHO, I think it really depends on your situation.  Which types of baits do you usually toss? If you find yourself flipping/pitching heavy jigs into cover, a MH-F 7' would probably be best.  If you find you like light plastics, maybe a M would be better.  

I fish with mainly lighter baits and trebles so my all around rod is a MF and in a 6'6" length due to length restrictions with my car.