Pricing rule based on the cover

Hello friends I'm a big fan of fancy product designer and I've been using it for about two years now I used to have genius but I've gave up on it since some features weren't working as expected. Finally it's been fixed with the removal background and by however, the big problem I'm having is calculating the pricing rule based on area covered for T-shirts and I'm really having a headache with this. I don't have any of you guys been able to solve it but I would really appreciate help and I would love if the team of fancy product designer will develop another plug-in. They were just deal with pricing rules. I think this would be great and I'll be a big fan. Hope somebody can answer me and looking forward to hearing from you. Thanks so much.