I used to do a lot of strength training before, and I still have my old notes (Wendler), and taking into consideration that we have pretty similar physique I will guess that you can max out with 80 kg. Your shoulder are of course a risk here, and I do not know if I could recommend maxing out. I will not participated in the challenge myself, as I stopped exercising a few years ago. I am still in peak shape though:) Good luck!