Mass is hypertrophy. What I failed to say was 5x5 Bill Starr is strength first, mass second. I think is hypertrophy is your 1st goal there ARE better programs. I never said you can't use it.

Rest periods: I did 2-5 minutes depending on how taxing the effort. True hypertrophy routines use less than 2 minutes by some suggested rule of thumb :-/. This is again, why I said look for another program. Bill Starr is a Linear Progression geared toward strength, meaning larger rest periods and less hypertrophy than some pther programs. Can you do it, yes ? I just don't recommend fucking with the 5x5 program. It's damn good as it is.

So in sum, 5x5 = both strength + hypertrophy, but if hypertrophy is #1, there are better programs.

For all I know maybe you just mean an extremly basic 5x5, but whenever I come across 5x5 it is Bill Starrs intermediate or advanced model.