Issues after moving to another bike

I've been running a Vector 2S on my winter bike for a few months, competed a couple of CP20 tests and established a pretty good idea of my power levels. 

I moved to my summer Triathlon bike. I used a torque meter but, despite being a big guy, I failed to get the torque meter to "click" - though I am convinced it's pretty damn tight! I've calibrated correctly, checked the crank length (which is slightly shorter on the Tri bike) so all should be good. 

The power readings are significantly lower. The data below is from two recent Strava PRs (same flat/hill) to show the difference:

23/4 3:35 169bpm 234W
13/3 3:43 169bpm 345W

Now, it's perfectly possible that the issue was with my previous set up but if I compare to a friend who's a similar size (but a lot fitter) he had:

3:54 150bpm 308W

also, are you supposed to hit calibrate before every ride

Any ideas?

Thanks