Woocommerce: Product with variations with different tax rates

I use variations in my single products to sell prints/originals without and with frame.

At this moment I would like to sell more originals but they have a different taxrate here in The Netherlands then the frames.

How can I use two tax rates for one product (with two variations).

When I adjust the tax rate per variation it doesn’t save that adjustment. It keeps changing the taxrate to the “Hoofditem/Main Item” tax rate.

I have a few products that consist out of “Original artwork” 6% tax and “Frame” 21% tax.

Ideally I would have a price/variation for the product as 1. an “Original artwork” 6% tax and 2. “Original artwork” 6% tax + “Frame” 21% tax.

Thanks for your help! Driesje

http://www.galerietje.com/winkel/gepersonaliseerde-mejuffrouw-muis/