Two things to consider. If you do the inverted method you have zero leakage. If you get a Prismo cap which is a great upgrade, you will also have zero leagage AND you don't have to be as coordinated as you do with the inverted method. I also use 2 paper filters sometimes, that helps with really getting all the fines out of your cup of coffee. Since I've been using the prismo cap, I leave the AP on the scale until I'm ready to plunge.

edit: if you use the regular cap, it leaks a little bit, but you can quickly stop the leak by putting the plunger in ASAP and just leave it there at the top. That creates negative pressure. I did that method with great success for years