two new bathroom groups, same floor. (Canada)

[Willie Two]

What is the best way to connect two toilets that are almost back to back on the same floor to a common 3 inch stack/vent, I have almost 5 feet of vertical stack to tie into. I am thinking one connection on top of the other ?Thanks.

 

[MikePlummer]

symetrical connection (double Y) then you don't need to ven either providing there aren't other WC's upstream