Well, I think you'd be fine with the reps of 4 on the rapid wave to gain size just fine. It's like if you take the traditional 3X10 method but reverse it to 10X3, then you have the same amount of volume (30 reps total) but with the lower reps per set, you can use a lot more weight, so that the intensity (closeness to 1RM) is high. Plus, with the way rapid waves are set up you get a nicely aggressive so that you cover a wide spectrum of recruitment and this is important for muscle growth.
But pyramiding has no set in scheme, so you can tailor it to how you want. There's really no wrong or right way. However, it is generally accepted that size goals, start heavy and work up-1X10, 1X8, 1X6 or 1X8, 1X6, 1X4 and visa versa for strength goals (in the case of single waves). Just for kicks, let's say I was doing a chest/biceps day, it might look like this-
A)bench:1X3, 1X6, 1X3, 1X6, 1X10
B)1 arm incline db press:1X10, 1X8, 1X6 (last set to failure)
C)cable flyes:5X8-2 second pause at the full squeezed concentric (last set to failure)
D)bb curl:2X6, 2X5, 1X10
E)seated inc hammer curls:2X8, 2X6, 1X5 (last set to failure)
F)reverse curl:1X12, 2X10 (last set to failure and slightly cheated)
This kind of set up would add strength to go with the show. As you can see, I'm more of a fan of wave pyramiding. It allows you to be creative, vary the tension, and not lock yourself into a certain set/rep scheme.