There's a few mentions of B5's and solo seats - here's mine!
I ordered both the Old-Fashioned Solo Seat and the Deluxe solo seat from NField Gear, planning to try out the looks and feel of each. I found the Deluxe comfortable in exactly one spot, with no allowance for changing position. The old-fashioned lets me slide forward or back just a little bit - enough to tip the scale in the comfort department.
I like the look; I have an motorbike-riding friend visiting from Scotland, and he says for looks it's no contest, the old-fashioned. I think he's right!
And, I love the springs - they really ease the ride after the hard factory B5 seat.
The build quality leaves room for improvement - The holes in the brackets that mount the springs to the frame line up perfectly, but the angle wasn't quite right, so when I tightened down the "vertical" nuts holding the front of the brackets, the brackets bent to conform and their paint cracked and chipped. Also, the seat's frame is crooked enough that I had to stack a pile of 1/4-20 washers on one spring to level the seat on the bike - see photo.
So far, though, I'm happy with the looks and the comfort!