Hello
I have the bench plus so not really sure about the normal seats, but all I can think off is folding the 60 side of the 60:40 seat flat and doing it that way. Or I think that Audi actually do a ski bag, this is a hole in the middle of the bench (hidden when not in use) with a bag attached to it so as you push skis through from the back they slide intothe bag and keep the inside of car nice and clean. Not sure of cost, but it may be cheaper than the bench plus?
I'm sure others may have some other ideas on how to achieve what you want?