Yeah, I did it about a month ago. Definitely want to shorten them at the handles. Actually, I called AAA inflatables of Denver and they told me everything I needed to know. There is an inner sleeve in the shaft down there a ways, so the handles don't just slide back in. Got to sand them some. Or, as I finally did when I got sick of sanding, file them quite a bit. Basically ya cut to desired length (remembering to account for the length of the handle, too) and then use a dremel or cutting wheel to make a lengthwise cut in the part ya have cut off. Got to be a little delicate so's to not cut into the handle, but then after all you will be sanding this part later, so it's not all that touchy. Handle comes out easy, really. Ya cannot buy a replacement handle anymore so ya must do this part.
I went ahead and got some shot and put it into the hollow handle, with silicone to keep it from rattling, so as to counterweight it a little. Was a pain to find the shot, and didn't really make that much difference.
I used a hair dryer to heat the shaft a little, and put the handles in the fridge for an hour, once they got to be a close fit. Used a rubber hammer to help them go in. I don't think they'd ever come out, but I used a couple screws to finish it. Drill a slightly bigger hole in the metal first, before you put the handle in (since it won't come back out) and then the sheet metal screw will easily pass through the oar shaft and engage into the handle. Piece of cake.