So, I’m about to swap a pair of forks, the headset on the bike is a cartridge bearing job. The crown race is a non-split one, and everyone knows that split ones are much simpler to remove/install.

What’s to stop me cutting a notch in it after I take it off the old forks to make it into a split one, so making the installation on the new/subsequent forks more simple?

been done recently – I’ve done it, as have loads of others to no ill effect.

none whatsover in my opinion.
(assuming you’re using cartridge bearings and it isn’t the actual “race”)

nowt* – i do it to my CK ones – makes it all a lot easier.

i doubt it actually makes a difference, but i cut mine at an angle as opposed to straight in (if that makes sense).

*i am not an engineer

I’ve done it as well with no adverse effects. Use a junior hack saw so the cut is as small as poss.

Super, thanks chaps

How often do you need to swap it over? I think it’s actually quicker to bash it on and off a few times than cut it.

more simple

or Simpler?

Anyway its probably best to leave it intact I’d have thought,

The Taper on the Crown race will have been designed for full face contact with the bearing surely…

You are effectively proposing to lop a small section out of that face, yes it will be under compression but loading will not be uniform (and might be marginally eccentric?) and if it bolloxes your headset/fork then you will be entirely to blame, all in order to save a bit of time on a possible later change of forks, really worth the risk?

I find it depends on the headset and fork type how tight it is
A non split FSA one slid onto my rockshox’s no problem but a CK one was really tight