I use a 6" drop on my snowmobile trailer.

 

Ok, so while i'm waiting for my atlantic british wiring kit to arrive, i purchased a Reese Ball mount at Autozone and put into the hitch. This 'standard' shaft length however seems a little short (guess its 8"?) IE the ball seems awfully close up under the bumper. Seems like i would need one with a longer shaft length to extend a little further out from under the bumper. Anybody have any thoughts on this? Looks like they make some longer shaft lengths, like a 12 inch. But these dont seem readily available at the autoparts store or the auto section in walmart.

 

You said shaft...hehe...hehe...

The only problem with a longer draw bar is that you reduce your tongue weight capacity.
Its that whole physics thing, the farther out from the main support you are the less weight you can carry because it gets multiplied and puts more stress on your trailer hitch.
I would wait until you get the boat to see what you actually need, try the one you have and see how close the boat is.
If you need a different length you are going to have to go to the camper trailer supply store.

 

Short shaft is perfect, just get the correct drop. I would rather have the ball closer to the hitch.

 

you can get long hitch shafts at JC whitney and harbor freight