Again, thanks to everyone for your help. A set of scales won't break the bank and I will invest to check the dipper charges.
In the meantime, given the information above and from others, can I please ask again whether the simplest idea, using the 3.1cc dipper to produce a charge in the middle of the load data I quoted, be doable? Or is that too risky given the size of the dipper compared to the Lee recommendations?
I went through this exact problem. What I did was invest in the dipper set and work up to the next whole dipper using combinations. So I think the initial load was 2,5 cc and I now load 2.8cc. But I loaded 2.6 and 2.7 using combinations and worked up. From memory this worked out at around 90% of the max load listed in the manual.
I did use some scales to practice my "dipping" though and get great accuracy but a consistent technique is the key.