I do. I have two Reed 3P's. See my profile. My advice is to not sweat it. You do not need inserts, assuming an armboard of say 3/8's or greater of hardwood. As I have stated multiple times in this forum and only had agreement from the experts here, P-S is not an exacting spec, assuming a slotted headshell. Your cartridge and stylus have no idea about and don't give a crap about P-S so long as the stylus hits the desired null points. Proof lies in the modern SME methodology. With modern SME arms there are no headshell slots-the cartridge can only be mounted in one fixed position and the solution is to slide the tonearm mount closer or further back-CHANGING the P-S! There is an invaluable lesson to be learned by the SME method of obtaining alignment. The take-away is that as long as the cartridge can be fixed in the headshell to meet your two preferred null points you are perfect.
The exception COULD be if you rely on an alignment tool similar to a Mint Protractor that is custom made to a given P-S. In that situation, without exact P-S, your custom made protractor is of little use. You can still get perfect alignment using a universal tool like Feickert's though. So let me say it again-with a Reed 3P you can be 2-3 mms off either too close or too far and be fine with most cartridges. Beware too of cartridges that have abnormally long or short cantilevers.
The exception COULD be if you rely on an alignment tool similar to a Mint Protractor that is custom made to a given P-S. In that situation, without exact P-S, your custom made protractor is of little use. You can still get perfect alignment using a universal tool like Feickert's though. So let me say it again-with a Reed 3P you can be 2-3 mms off either too close or too far and be fine with most cartridges. Beware too of cartridges that have abnormally long or short cantilevers.