I found it reasonably easy to stay "aero" for the 25 minutes. Weirdly, I haven't made any adjustments to the bike from the ones the guy I bought it off was using. He was exactly my height. Back in 2011, I had an expensive bike fit but never felt as comfy as this - although maybe comfy is not the fastest
2 weeks ago, I put out my best ever 26 minute power doing the TT on my roadbike (282W). This time I felt as if I was working as hard, but put out 263W.
The next 4 weeks TTs are using a 20km route, so we'll see how that goes. Next Sunday I also have the BMCR race which is a 16 mile TT but on roadbikes.