Well, the seatpost change went pretty smoothly, the new post definately reduces the height of the seat by over an inch.
The original post held the seat by the rails, but it held them at the top of it's height. The replacement is a different style, and I have it holding the rails down low.
Replacement on the left, original on the right:
So, with the original post the seat sat like this at it's lowest possible position:
The replacement post drops the height by over an inch:
Here's the old post next to the (installed) replacement. I tried to hold it at the height it had been installed at for comparison.
Not bad for five bucks, and Harley's happy with it.