Can the 5x5 and 7x7 can not be centered on the square they are mining but in the second block (from ground to ceiling) so you can mine in a straight line? (in the 5x5 would be 1 block below the one you are pointing to, the block you are pointing to and 3 above that one). Or that this could be an option (an offset value)?

You can offset it in the shift click gui. It defaults to automatic but can be changed to tunneling