I seem to always have blocks that turn out smaller than they should.
As long as all your blocks are the same size it dosnt matter.
Just make sure to adjust your sashing to fit your size blocks.
If your blocks are to big do not cut off your points just to make the block the size the pattern calls for. Use the larger size and adjust your sashing to the size you need.
Size dosnt matter, its the points that are more important.