Extra optional custom fields

[GrahamNR17]

This is pretty confusing, so may I seek your counsel on correct usage?

I've created a product, sewing machine needles, which I hold in different sizes and have different quantities of each size.

1. I create and save the basic product information with photos etc. I set the shipping to fixed cost of 0.90 and seect the Count shipping only once. I do not set requires stock (or regardless of what follows, it shows as out of stock). I save the product and then edit it again.

2. I then create a Custom Field called "Size" with Text>Select Box as the type, Required: Yes and Requires Stock: Yes, Stock Qty: 0. I then save everything and go in for a re-edit.

3. I then select the [Manage Select] and create some options, eg a Select value of "Size 16/100" with  Requires Stock: Yes, and Qty In Stock of 1. I repeat that for several other sizes.

4. After saving and going back into Edit, I can see that the Qty down in the Extra Options area is displaying the correct stock quantity, so I reckon everything is good.

The I can go to the product in the store, select the size I want from the drop down, and for that product set a quantity of 5 and add it to the cart. All five are added to the cart, but there's was only Qty1 set as the stock level for that product.

If I then go back and select another size option and add that to my cart also, it adds another shipping charge for that too.

Am I using it incorrectly? Should I be doing it differently? Am I even making any sense? 

I'd welcome your guidance 

Best,
Graham

[GrahamNR17]

Might there at least be a work-around for this?