Thanks Greg for the PDO. I have thickened the shell and smoothed it where possible.
Not sure if it will be wearable due to some of the cavities inside, but I have done all I can.
I tried a couple of options on how to prepare the model so you at least have a couple of choices and I've included the original conversion also for those that would like to have a go at improving on it further. Good luck with your sons project and post some pics if you do take the challenge on, Cheers Jace