i showed the prototype to my friend that is making this for a kid he looks after and they both freaked. the kid is going home on spring break wed and wants a hand full to take back to his mom and see if they will sell them or what. if you cant make wednesday happen i understand its an impossiable time frame. colts father died about a year ago in a plane crash, and when asked about putting something on the back he want "always be # 1" i think it was something scoop(his father) always told him. they are really big into horse racing and the baha 1000 in mexico.
i dont know if this would work or not but if you could mirror the image and then cut a female toolpath of it so the cut part will sit in it upside down. and weld that to a small sheet and clamp that down to the table and use a really good magnet on the back and see if it would hold it in place while engraving the back.
let me know what you think, and if you could price out 5 of them.