I find determining seating depth for best accuracy a lot easier with cup and core bullets.
Monos, any brand, can be really pissy about seating depth in specific rifles. The best I have been able to work out is that you have to not only account for seating depth by itself, but also the effects of fouling, specifically copper fouling. I have solved more than fifty, maybe more than 75 rifles now for monos. I always use the Hornady (Stoney Point) gauge and comparator.The only "shortcut" I have found with them is start at ~.050 off and work up to best accuracy/max load. Sometimes that's all it takes. Usually to get MOA/sub MOA, I need to adjust depth. I have learned that I cannot begin to predict What a rifle will like. What I do is to bump them out to .010 or .005 off and start working back in .010 incements. I do not recall having found any that were out past .150 off. I have fount a couple that were close though.
One thing that I have also learned is that the "classic" 2 and one pattern doesn't mean much if anything. Normally that pattern is a signal to adjust seating depth. Monos are extremely consistent bullets. The don't have voids in the core, they do not have wrinkles in the jacket. They are vastly less susceptible to damage. I find that if I get down to less than 3 inches and just cannot shrink the groups any further it is best to go looking for a node. I have a 26 inch Sendero 25-06 that should produce 3400or a little better with 100 grain monos. It will do almost 3500with carefully selected loads, but so far I just cannot get to MOA at those velocities. By accident I discovered the barrel is flat out accurate. I bought a few boxes of Black Hills Gold ammo really cheap for the bullets and cases. On a whim I shot a few. Well under and inch! So, I immediately started with the measuring. It showed me that the difference was solely velocity. The Seating depth is identical, Case length identical to what I had worked up. I backed down the loads to a very pedestrian (for this rifle) 3225 and there it is, sub MOA. Normally, I will not chase velocity. This rifle was bought for one purpose, to move a 100 grain bullet fast and deliver all the velocity possible out at 500 + yards. The project now has been reduced to finding a powder that produces 3400+ and allows that barrel to produce a node there. I even went so far as to try a donut on the barrel to see if it would help. Problems like this are where Quickload can help.
