Centre-edge magnetisation is considered to be less effective than corner-edge, for two reasons. One is that the centres are already holding the edge pieces in, so the magnets don't do that much for stability. The other is that centre-edge magnetisation has a smaller radius than corner-edge, so even if the force is the same, the
torque is smaller. (Smaller radius also means the angle over which the magnets attract is larger, which makes it less clicky. This may or may not be desirable.)
Do magnetise it if you have some free time, but set your expectations accordingly. It's probably not going to become amazing just from centre-edge magnets. Also, be careful when magnetising the centres; I hear it can be quite tricky to avoid having all five magnets just fly towards each other.