So tell me if I have this right.

1) The two extra countersunk holes in the middle are for mounting a balancing weight/lipo stopper - yes?

2) the extra two under the motor mount are so you can mount the mount () with either 2,3,4,5 or 6(in theory!) screws and vary the flex?

3) from the spacing shown with the split blocks (note the chassis keying), you could still elect to run 1 piece blocks?