So I've actually done something along these lines with my own product.
I put it up as a pre-order with a deposit, with the delivery month stated clearly on the page. And only committed to production once enough orders had come in. The mould money stayed put until the orders showed their was real demand.
Your step with stock at 0 and backorders allowed does work as a quick test. But it won't take a deposit. Customers either pay the full price or nothing, so you learn less about how serious they are.
Bear in mind the pre-orders extension you linked doesn't split the payment either; it just moves the moment the full amount is charged. For a real deposit you need a separate deposits add-on on top, which is what I ended up using.
Whichever route, put the delivery month on the page. If the orders come in, you have your answer. If they don't, you've lost very little.
