I have run into an issue with stock control.

I need to control the stock at product level but also by options at the same time.

I have pendants and chains, I only stock so many of each length chain and I just add the chain to the pendant when I receive an order.

Example scenarios

I have 2 chain lengths available, in 16inch and 18inch and I have 2x 16inch and 4x 18inch in stock.

I have 2 pendant styles with 3 of each in stock.

So I have enough chains to supply one with each pendant for sale, however here's the problem.

If I set stock by product, someone could order 3x pendant style 1 with a 16" chain (which I wouldn't be able to supply because I don't have enough 16" chains).

If I set by options, they could order 4x pendants style 1 with 18" chains (which I can't supply because I don't have enough pendants).

The pendant styles can be significantly different, it's not an option to put them in the same listing (also this is a simplified scenario, there are actually about 50 pendant styles and 4 chain lengths).

So how can I manage this?