MIlling slot size

hello,

i see on the capabilities page

to mill a slot inside the PCB area say a half circle

the std mill size is 1mm ?

can it be 0.8mm ? or 0.6mm ?

for example to make for very high surface resistance at opamp input > 1Tohm

the SOIC 8 pin the width is only 1.27mm

if i make isolation of 1 pin using 0.8mm

there is only 0.47mm left

to put a isolation on the + input pin

you know what i mean ?

tyvm for answer