Hi officemike,
Maybe you can do that with characteristics. And for each variant, in that case each store, a different quantity.
You can try:
product_vendor_id, product_code, product_name, price_value, product_quantity, product_type, store
2, 50707, item_name, price, 25, main, 2
2, 50707, item_name, price, 25, variant, 2
3, 50707, item_name, price, 12, variant, 3
4, 50707, item_name, price, 8, variant, 4
6, 50707, item_name, price, 0, variant, 6
For the store column, instead of the store id, you can set the store name.