Shawn,
Size of the cells on the starter strip have no bearing on the size of the cells the bees will build on the new comb. This is a misconception many people have and they go out and by small cell foundation for their foundationless frame starter strips. Yes they will draw the first couple cells to match the starter strip, but will then transition to the size they want. If it were as easy as giving them a cell size and they would just continue with it, regression would be just one step. Unfortunately this is not the case.
So yes, go ahead and cut those plastic frames if you want, they will build comb the same as if you gave the small cell starter strips, popsicle sticks, etc...