Well, my brain didn't thank me for thinking about this! You can certainly cut down the 7" size. The effect of this is to change the proportions of the block slightly, since you end up with slightly smaller circles in relation to the rest of the block. Considering the cost of the companion set for the 12" Qube, though, I'd be just fine with smaller circles! I personally think both the Qube and the companion sets are very over-priced.