I have a product of a wooden board with all different sizes and different prices. All prices need to be including 19% VAT. What I did was adding a "shopping cart variable" at "custom fields" and put in a line at "standard" inputbox and "in list?" and "add to shopping cart" ticked.
at "standard" I put in:
1,9x20x40;2,9x20x40;3,9x20x40;4,9x20x40; (etc etc... untill I unfortunatly cannot exceed the 255 chars. Or I am doing something not intended here, I suppose. Or the line needs to become a textbox) Anyway... for this part it works functionally except for getting stocked, but happily I don't need that with this customer, else I was screwed... ) Now... I made a VAT amount of 19% as mentioned earlier. This amount is calculated correctly on the prices except for discounts for "shopping cart variable".
When I put in for:
1,9x20x40 -> 1.10 (1.10 euro added ON the default product price.)
2,9x20x40 -> 1.20 (1.20 euro added ON the default product price.)
3,9x20x40 -> 1.30 (1.30 euro added ON the default product price.)
4,9x20x40 -> 1.40 (1.40 euro added ON the default product price.)
the price in those above here needs to be put in EX VAT. So if I put in 1 there, the frontend tells me 1.19 (oke, not the biggest deal, but it whould be handy if I could put in the amount INCL. VAT also optionally like in the article page itself is possible)
Untill here I don't meet much problems..... but then shit happens 
When I make a discount for the product, for instance lets say 2 euro. I want to be able to choose on which of these wooden boards the fixed discount applies to. (with a check marker?) It now seems that all other dropdown menu items have an increased discount amount?!. So my 2 euro discount for default product becomes 2.20 for the second instance. Oke... what I did was, assuming the above shopping cart variable method isn't suited for this matter. I choose another custom field to test.... "plugin". I noticed 3 options with childs etc... But then I can't seem to manage, reading all obove posts, to exclude the child items. I don't need child items. I just need a container with variable products. Preferably with no root price and discounts on choosen variable products.
For now I met 2 problems:
1. with shopping cart variable the amount of input at standard is 255.
2. with shopping cart variable the discount is miscalculated for all other "shopping cart variable" products.
3. with shopping cart variable the amount put in at the product its custom field is ex VAT only. (even hikashop has this option to choose between inc, exc)
4. maybe the most important when choosing a discount is that the price amount stays the same, also with a larger size of wooden board

(can;t be good

)
note: (instead of using the custom fields I tried sub products, but those are buggy and doesn't show up in the website at some child level below the product or in the categorie, it doesn't show me a price in the overview but does in the details and is also to complex for every different size being put in for each different type of wood)