Mark-B
Experienced
I’m not sure if I want to go through the process of making my own nut. I may just have to make the 4 hour drive to have a luthier take care of this.
It's just widening the slots - running a hundred-bucks of files through them ...once ... :0) ...But if you get the angle wrong then you can get twang and other such problems.
I seem to remember that my last Strat came strung with 9s? I installed 10's straight out of the box and wasn't overly impressed with tuning stability (pretty horrible as I recall). I replaced the stock nut with a brass nut - but you have to shape and contour pretty-much all new nuts (even Fender nuts), which can be a PIA if you don't have the right tools and equipment, And size the slots.
Like you say.. You can forgo all the fun-stuff if you know a guy .. :0) ..
Best of luck with it.