I wanted to use the strongest magnets given the constraints of the HSW system. I found these magnets (unfortunately they use imperial units):

• 9/16" dia. x 3/16" thickness
• grade N52 magnetic strength
• https://www.kjmagnetics.com/proddetail.asp?prod=D93-N52

Modified the insert to accomodate as above. This allows the magnet to sit flush with the honeycomb wall when mounted against the refrigerator panel. Allows for press-fit with tolerance. Hole on reverse side allows for pushing the magnet out should you wish to recover it.