DATURA. STRAMONIUM
This combo doesn't intensify his trip in SWIM's case.
In fact the journey becomes less potent.
It counters the mushroom effects.
For example, SWIM always turns off room lights when on mushroom alone,
because it feels too bright to him probably due to pupil dilation.
But when combined with D.Stramonium, this doesn't happen.
He can enjoy his trip under bright room lights.
And Datura doesn't add anything special.
So this combo is simply a bit awakend version of mushroom.
But It has it's advantage.
He can see his experence from a different angle, with a sober mind.
It's like somone in SWIM is awaken during the trip and says
"Wait, is this worth crying over the emotion at this moment ?"
I can't recommend this combo indiscriminately to everybody
because this get rid of emotional explosions which is characteristic
to mushroom and reason why people like this psychoactive.
But if you want to understand your journey without the confusions
( which almost always comes with mushroom to SWIM ,especially on high dosage,
where he can't figure out what he is feeling),
I recommed this combo.