@Unknown Munitions
Please dear God don't make it super short "for the kids" they are a tiny part of the market and one that will outgrow the product eventually.
Making the product worse for 90% of the users to help a few is a hassle. I don't want spacers or atleast not excessive amounts of them (You have already found most like more than 13.5" LOP in the regular rokstok). Every single kid will outgrow a small stock but adults won't. If the youth are a big enough market make a youth specific stock (doesnt seem ultralight is a benefit to youth and the reduced height above bore also doesn't help so a dedicated youth mold to suit the largest range of actions in a single mould makes more sense to me).
Too much versatility often comes at the cost of being good at the main task.
That's why the Rokstok Lite exists isnt it? It's more heavily focusing on weight where that focus would take away from function on the regular rokstok?
Edit: I'm hoping I misread above and that you meant a second 12" LOP for kids only