Found by reducing the restrictor to 1mm = .039 thou i gain 15 psi pressure up to 75 -85 when at 3,000 but oil now only squirt 1/2" above the rocker hole then runs down the top rocker groove giving the roller tip a good coating of oil
Will increase hole to 1.5mm .059 thou should give a good result this is a oily vid at .094 thou at idle.
i would be concerned that going much, if any smaller, you could possibly end up with that hole plugged up over time.
Think where you are at now is probably ideal