Alternate Size Variations

Hi,

I am trying to set up a site using woocommerce that sells jewelry, in particular rings.

I want the customers to be able to choose a sizing system from a drop-down i.e. UK or US sizing. Then, depending on the sizing system chosen I want the Size drop-down to show either UK sizes or US sizes, but not both.

I have tried creating variations that have the UK size system then individually assigning each UK size with that system and the same for the US system. However there are in excess of 70 sizes for each system making it unmanageable when adding new products.

I have also tried creating attributes that have the UK size and the equivalent US size in one attribute and doing away with the size system choice, but this becomes messy and confusing in the drop-down list with both sizes next to each other in the list.

I have looked at Ninja Forms and Gravity Forms plugins but I am not sure they can address this particular task or not. Maybe someone who has experience with these plugins will be able to answer this?

I would be happy if someone could point me to to an example where this type of thing has been implemented and how, or if there is a particular plugin that can address this.

Cheers,

Paul