Yeah, late to the party but it's a little much. I haven't done a full set but did do one quite recently, took a little over an hour (think I invoiced 1.25) of my time and I had to enlist the help of my thin armed boss for about half an hour to buck a couple of the rivets I couldn't cram my arms into the floor quite far enough to reach.
So if I were to do a full set of 4 I'd probably fall between the two estimates of 5 and 8 hours, but I think that 2hrs per is a good guess ahead of time to leave some room for a SNAFU that isn't of my doing.