Plus4, Extension for Plus Plus Blocks

Plus Plus are wonderful building blocks from Denmark. http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=plus+plus They pack small and are perfect for playing while waiting at restaurants.

My 7 year old wanted an additional shape block to complement his Plus Plus set. He explained that the block needed a hole in the center. He designed the Plus4 part and I adjusted the tolerances.

The Plus4 fits well with the original Plus Plus. Unfortunately when made wi