Based on LionPrint's model from Thingiverse.

I've made some changes to the model to make it easier to print, as well as cut it down and arranged + manual supports where needed to fit the print bed of an A1 Mini.

The original author mentioned to scale to 135% to fit an adult, my model here is scaled to 130% and fit me perfectly (you can see in the 3MF file that everything is at 130%). I've also included a “head fit” small fast print cross-section of the helmet (plate #4) you can scale further and print to see that it fits your head well before committing to the larger print. you don't need it for the final helmet. I've also left a full model of the helmet outside of the plates in case you want to use a 3rd party “head” file or your own 3d scan to find the perfect scaling size for you.