Trust me, the weight difference would be ridiculous between cpc and the leaded pick hobsons. They are absolute bricks. It might be worth considering though since you’re definitely right that they would not be used in stacks.That's definitely true. Won't be easy to find. How about a small custom cpc scrown order just for the $500s? I understand the feel/weight is very different, but visually it would be way more appealing to me at least, to have some proper spots. And if it's only for the top denom they probably won't see too much play, and you likely won't be sitting with barrels of them in front of you. If it's only one or two in each stack, or a small handful in the biggest stack, the weight difference might not be too noticeable? Just thinking it loud here... And by the way, you should go all in on those amazing hundreds and buy as many as you can!
I would live to buy more 100s but those are also not easy to find