The measurements were taken with 12ies that apparently ran longer than some other brands. RTR has small metal shims that can be installed behind the pin in the adaptor (between the pin and the body where the little black oring is) that fix the leak. If you didn't want to go that rout you could also get a second one of those black orings to put in there.
Either way those two ways of fixing it are both deals that you never have to worry abotu it again unless the pin goes bad.
Most that went out after the first batch had these shims in them already, since the problem was caught within days of the first ones going out. It's possible that the shims are not on yours or that you need to add a shim.