Such variables will exist equally for the BIR kitchen as they do for the rest of us so i wouldn't get hung up on that.
As a ball park figure i would always use 1kg of onions peeled weight when making a base, give or take a little bit, but 350 grams is more than a little bit

. The spuds and carrot are in the ballpark ratio. I don't think your resultant curries will disappoint but i would reduce your normal spicing as your base this time will be on the spicey side. If you haven't frozen it yet, i would cook up 350gms of onions and puree them and add to the base to fetch it up to even out the proportions. By doing this, if you can, it won't impact considerably on the overall result

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As for chilli, i never use it, in mix powders or in bases. I prefer to add when cooking. That way i am in complete control of the heat. Being a chilli head, what isn't hot for me is for others. This reduces the risk of my feeding somebody a curry hotter than they actually like ;D
hope this helps. Look forward to hearing your results Bamble