I'm planning on upgrading to a bigger chainring and going 1x. Right now I'm running a 50t and I have to go over 110 rpm all too often. Since I have a 110 bcd anything other than a 52 and I'll have to buy a new crankset. I'd rather not but a 53 does seem like best option (a 54 seems excessive). For the 40k, I'm hoping to average somewhere between 260-280 watts.
Below is a table for my top end, I'm not looking in terms of average, but those 1-2 minute stretches where you're on a downhill with a tailwind.
Gear @90 @110
50x11 32.04 39.16
52x11 33.31 40.71
53x11 33.94 41.48
54x11 34.57 42.26