I've made up some of the big dominos for the 700 domino machine. Partly to save money but partly to get the fit I want. It's a little known characteristic of dominos but, odd as this sounds, they don't cut the same size mortice in end grain as in long grain. Cutting into end grain tends to push some of the fibres to one side, which spring back after the tool is removed so the mortice is a fraction smaller than the companion mortice cut into long grain where the fibres are severed cleanly. You'll probably have noticed that dominos tend to be gripped harder in end grain rails than in long grain stiles. It can be a nuisance with 6mm x 40mm dominos, but it's a potentially bigger problem with 14mm x 140mm dominos.