Best Rim Inner Width for XC

[irideti]

I've been running 2.25 tires on my hardtail for decades but might try 2.40 in the future. What's the optimal inner width for these tires? I just had spokes cut off on my old wheelset since the rear Stans Crest Mk3 have crack around nipples. These rims have 23mm inner with. I'm planning to reuse those lovely CK hubs. My wheel builder told me to get a wider inner since wider 'pinches' tire less for more optimal shape. Should I go for 24, 25 or even wider inner?

I know this forum loves BTLOS but I'm still debating between BTLOS and Lightbicycle.