FILLMESH is an MCEdit filter that fills in missing blocks in your creation that may be introduced through rotation, scaling, or other transformations.

It works on your selection box (except the outermost rows and columns), detects holes, and adds the block you specify in.

You can configure the number of neighbour blocks to recognise before detecting a 'hole'. In testing fixing holes in a roof, 3 was the best number.

There is a remaining glitch where some shadow blocks are placed near the corners of the selection sometimes, so be prepared to clip these out after finishing your edit session.

If the filter fills too much or too little, simply 'undo' (CTRL+Z) before saving and try again with a different parameter.

This filter is specialised to this particular task, however I have seen that it will 'round out' a square build, so you may find a use for it in adding detail to large models.

Enjoy, and let me know your results.