Dose - Diazepam: How closely does increased dosing adhere to increased effect

[GreatWonder]

Simply put 10mg of (Roche) Diazepam (Valium) does nearly jack shit for SWIG. SWIG knows the answer will be different for everyone, but if 10mg does nothing for SWIG, will the effects of 20mg be double the 10mg or if SWIGs tolerance is topped just slightly, can the effects hit harder (ie could SWIG suffer the one beer too many effect and go from sober to slaughtered).

I know SWIG should just try it - SWIGs thinking it's not a particularly huge amount, but just wondered if any SWIYs had experienced a huge difference between 10mg and 20mg (or doubling their usual dose of a similar benzo).