Update: I survived.
No clipless moments (few close calls!)
Knees felt stiff after 10 minutes. Adjusted cleats but didn’t change much. Stupidly adjusted saddle cos it was the same feeling that I get if my saddle is too low. Then my back started to hurt. Readjusted saddle and cleat angle and that seemed to help. I desperately need a professional fit, but that’s another story.
Anyways, once they were sorted (ish) I was floating. Hills that I used to dread or feel dead at the end of it didn’t feel as bad. In fact, there were some points where I realised “oh wow that was a hill!”. Didn’t notice it.
There were times when I crested a hill and went to shift to the big ring, but realised I was already in it. I spent much more time in the big ring than I normally do, and that was totally subconsciously. I just didn’t feel the need to naturally shift down like normal.
My calves feel more tired than usual - not used to pulling as well as pushing I guess.
And get this; I’ve not been out on a 10+ mile ride since Feb because my bike needed badly serviced and we couldn’t afford it until now. 6 months of no riding, and on my first clipless 26 mile ride I got 4 PBs on Strava. Each one of those was a hill that I used to struggle with.
So yeah, biggest difference was on hills, and what a difference. I’m a believer. Completely converted.
Edit: just looked at Strava details. 2 minutes faster on the hills than my previous best. Wow.