but is it possible to invest if the investor contacts stunna personally?
Its never going to be possible. PrimeDice is one of the most succesfull dice site around and everyone would love to have a share of PrimeDice. Stunna and his private group manage to secure this site and fund the bankroll in the past, I doubt that they would want to let another people to put in some investment and share the profit of it
If you have his personal contact info and you want to try to convince him to take your money as an investment, go for it! Lol.
I doubt Stunna will agree, Basically why would he want to share this site's profit to stranger while he can fund the site by himself and his private group though.

Logic isnt it