My routine is bundled expressive stretching using a lengthmaster, and I'm seeing visual gains already. I dont need to measure at this stage because I know its grown. You need either a power assist or lengthmaster to perform expressive stretching properly.
Yes, they have always been theorized to increase gains, at the end of the day I have been one of the only guys who has been trying these long term - see my current progress thread - and it takes the weak link in my opinion out of the equation, which is the penis we see, the glans, and gets straight to the what we want to expand, the inner penis, and working the ligaments.
A bundled version is more intense, takes the skin more out of the loop focusing the majority of the stretch to the inner core.