I see that Trek sells the "seat cap" in 135mm and 175mm lengths... although they must be made of gold as they're $120. The bike appears to be fitted with a 135 mm.

My loverly Ultegra carbon pedals arrived yesterday. Using the quick "adjust your seat so your leg is straight when your pedal is down and your heal is on it" approach, when the seat height is maxed-out, that's the perfect height. Traditionally, that's how I've always set my seat height... or perhaps made it a little lower than that.

Is there any reason to think I'd need the seat higher than that? I went through CompetitiveCyclist.com's bike fit calculations and it suggests I should have a 58 cm (or thereabout).

The shop where I bought the bike will only do very basic measurements for fitment if I take the bike back. Anything beyond a basic measurement is $150+. At the moment, I don't see any reason why this 56 cm frame won't fit me, so I'm thinking I'm not going to go through the hassle of taking the bike back.