I rider I support, has been testing 26/650/29er timed, the 650 was a quick as the 29 but offered better cornering and more ‘snap’ out the corners so over a stage race will be less effort due to the slightly reduced effort to move the biek around. and is now running 650, his 650 with a low profile tyre didn’t quite fit in a set of Sid’s but did in the Fox f120’s.
The foxs were lowered in travel to keep the geo ok as well.
The difference in diameter between my 2.4 Fat albert evos on Mavic 819 rims and his 650 with the low profile tyres was about 10 to 7mm larger diameter for the 650.
Thinkinhg about putting 650 on the front of one of my bikes for a play too now.