That's a hard call to make. With rifle barrels I can run them between centers over say, 20 – 24 inches so you can get the barrel within a half thousandths figuring in how far the center cutting reamers pilots are out for pilot clearance and the bend in the barrels which is under .004 thousandths. I often run rifle brakes at under .004 a side on brakes but pistol barrels are different.
We used to think pistol bullets kicked a lot on exit or the gun recoiled into the bullet and that's why we had so many bullet strikes on comps. The truth is pistol barrels are so short that its hard to get them dialed in to dead zero. Trigonometry is not in your favor and most pistol barrels can't be run between centers so you have to run them in dual cats heads and use pins to dial in the barrel. Almost all pistol smiths I have talked to say that .007 per side or .014 overall is a minimum. From there you have to open the comp up a thousandths at a time until the bullets stop striking the compensator. I would say that if you wanted to be safe .010 or .015 thousandths per side or .020 to .030 overall is a minimum unless you are willing to pull it apart and rebore one thousandths at a crack it until it works. There are company’s that make barrel piloted reamers and I had a set of these and they would often allow me to go to .005 per side with very little risk of strikes.
If Its a clamp on style I think I would feel more comfortable at .040 thousandths per side. If you have plug stike gauges I would start at .010 per side and I would run plug strikes through the barrel after installation just to make sure. If the plug strike gauges go in without binding and there seams to be a paper thickness on all sides of the comp I would say go ahead. Then if you get strikes ream as required.
