Light backpack for kids?

Has anyone gone down the path of making their own light/ultralight pack for kids (i.e. pre-teens)?
I have been looking at options for my 7 year old, and the weight of the packs available is almost 25% of his max carry weight.
I'm looking around a 25-35L capacity, and keeping the weight below 500g (for a max carry of 5kg)
Is it worth exploring, or just leave it for now?
I have been looking at options for my 7 year old, and the weight of the packs available is almost 25% of his max carry weight.
I'm looking around a 25-35L capacity, and keeping the weight below 500g (for a max carry of 5kg)
Is it worth exploring, or just leave it for now?