Hopefully this gives you something to work from. The lower case are 3mm, upper case 5. I reckon you could just squeeze 3 x 5mm letters unless maybe your groomsmen have the initial WWW or something.
You're a star! I reckon the 5mm ones will be spot on and I may have to just keep the letters a little bit snug on the 3-initial one. Great tip with the vice too! I'll let you know how get on!
Hopefully this gives you something to work from. The lower case are 3mm, upper case 5. I reckon you could just squeeze 3 x 5mm letters unless maybe your groomsmen have the initial WWW or something.