I just experimented with the GOG gifting and promo function and discovered that when you own a bundle, you can gift also single items of it for the full discount, you just have to first click on "Yes, gift the entire pack." and then in the checkout delete the items you don't like with the cross on the left side that appears when hoovering over an item.

You might ask what's in it for you? A copy of Alpha Centauri. :)
Cheers

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Thanks a lot, redeemed :)