If you are experienced with both substances it should be fine. I personally love mixing dissociatives with 4 subbed tryptamines, there's a great synergy between the two. In highschool my usual dose was ~600mgs of dxm with 3.5 to 7 grams of mushrooms, always had a blast. More recently MXE/4-AcO-DMT as well as Ketamine/4-HO-MET have also provided great experiences. Beware that cannabis greatly potentiates dissociatives, this can be good or bad. Smoking on DXM or Ketamine shoots me into outter space where as cannabis mixed with mxe just produces a hour long panic attack.