Sportiva genius vs testarossa sizing.

So, I wear a 41.5 in the la sportiva testes... These shoes, the geniuses, do they stretch? They feel small compared to my testes. Would you size the geniuses the same as the testarossa?

I don't know versus the Testarossa but I sized them exactly the same as my Solutions (old version) and that worked well. Super tight at first but they stretched a little bit very quickly - despite the slingshot rubber- and now are perfect. Hope that helps.