a few months ago I had 19mg of 4-aco and 150mg MDMA at the same time (expecting the trip to be "heavy"). set and setting were perfect - safe.
the 4-aco kicked in as fast as it always does and I was comfortably floating in tryptamine-space for maybe 20min.
@45' the MDMA came into play and boy it was rough. it absolutely floored me - "count your breath and try to relax". very physical, totally immersive - not in a visual/visionary way but the experience was just so strong that it left no room for anything else but coping. reminded me of ayahuasca actually.
of course at this point individual factors come into play: this is your chance to go through intense catharsis/ecstasy/++++, if you are ready&willing. I was not, some of my co-trippers were and got a lot of benefit from this combo/dose. however it should be clear that this is for absolutely safe settings only and nothing for beginners.
the heavy part was over at "just" 90' and I was eager for the 60mg booster.
next time I'd go up with the tryp and lower the MDMA. 25 -110 maybe.
I bet the initial peak would still be immense but so are the benefits to receive from such an experience.
I would strongly advise against stacking the peaks in a non-safe setting. in this case I'd wait for the MDMA to peak, then take the tryp. maybe along with the MDMA-boost.
the combo (psychedelic) empathogen as a base and a tryp on top is an absolute winner in my books. just a few days ago I had 18mg aMT + 15mg 4-ho-met @120' and had an extremely pleasant (and social) day in the park. combos like that are also nice when dosed low. still looking forward to combining a full dose of 6-apb with a mid dose of 4-aco though. spiritual ecstasy inevitable.