Don't use donuts. The thickness of the donut throws off the balls wildly as very slow speeds and makes the game unplayable.
I use faber castells to mark the pin locations when I play 5-pins. (I have marked center table exactly with a sharpie and add the white dots occasionally) I've also used these pencils in public on pool tables and nobody has ever complained, though 5-pins with pockets is a much lesser game, but still can be fun.
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The width of the castle, according to the
UMB rules is 132mm. So the spacing of each pin is 66mm on center. Since a carom ball is 61.5mm and each pin base diameter must be 7mm, the clearance is 59mm between pins. Per the rules you need 2.5mm ball-pin total overlap horizontally.
If you are using pool balls and 7mm pins, just space your pins 66 - (61.5-57.2) ~= 62mm on center. You can print out an template with a printer.
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