I've had a psychotic disorder for just about as long as I've used drugs recreationally, and I think I'm pretty adept at knowing my triggers and knowing when enough is enough. So the advice I give will be heavily colored by my own experiences, which are in turn colored by my individual traumas, symptoms, physiology, tolerances, etc. Basically when you have a psychotic disorder you never know where your next trigger is coming from, so you'd best be prepared for any event.
So here's how I see it, based on the limited information you've provided: you're tapering off your antipsychotic but you want to continue to use recreational drugs? Can I just ask why the haste in tapering your AP if you're worried about a relapse? No judgement from me. I understand that these meds are not for the faint of heart. I would just like to understand your motive here.
If you would like to try using marijuana, for example, I would do it while you're still on a steady and effective dose of your antipsychotic. That just makes sense. Or any recreational drug, for that matter (that doesn't interact with any meds, of course). It just doesn't seem logically sound to alter multiple variables when trying to determine if you indeed have a chronic condition that must be managed with meds. In your shoes I would do the recreational drugs while on the meds, see how I react, and then decide my course of action re: tapering.
Here's a little bit of my background with this stuff:
I've been a long-term, multiple-time-a-day marijuana smoker since my late teens. My first psychotic break happened when I was 23 (I'm 32 now and haven't been hospitalized since 2014). I have taken several long breaks from weed with no change in symptoms. However, I find that when I'm hearing voices (which was about 75% of the time until this past summer - now I hear them only rarely), smoking weed really helps me cope. It calms my anxiety and helps me process difficult emotions. I find I'm able to journal better, communicate more effectively with my therapist, and have more useful insights into my voices' seemingly random jabbering than when I'm not stoned. Does that mean it's going to work that way for everyone on the psychotic spectrum? Nope. But it works that way for me, and, anecdotally, I have heard it from other members of support groups.
Alcohol, on the other hand, is a huge trigger for me. If I have more than a few drinks in a night I'll probably start hallucinating. Not so for many of my friends with similar disorders, though.
I have a personal dislike of opiates because of the way they usually make me feel physically, in addition to the losses of loved ones over the years to overdoses. But again, no judgement. They're just not for me.
I do an assortment of other classes of recreational drugs, though, with no ill effects as long as I keep my usage in check (which means checking in with a trusted loved one about my drug use) and an eye out for prodromal symptoms.
One thing that has helped me has been working on a Wellness Recovery Action Plan (WRAP) to pinpoint my prodromes and try to steer toward better habits when I notice problems arise. Here's a PDF with a basic WRAP outline. You can adjust it to suit your needs, of course.
http://www.workingtogetherforrecovery.co.uk/Documents/Wellness Recovery Action Plan.pdf
With a WRAP, you can train yourself to notice small changes in mood and behavior that may signal an episode. Combined with journaling, this can prove to be an invaluable tool in figuring out which drugs, if any, are okay for you now, post-psychotic break.
I feel like everyone without a psychotic disorder has an opinion on whether we should be doing any recreational drugs at all, without knowing any of the actual theories or models of the neurology of psychosis. And it's often forgotten that we're still intelligent human beings who can make decisions for ourselves... it's taken for granted that everyone "deserves" access to potentially mind-opening experiences except those who deviate from a prescribed norm.
Psychosis isn't the end of the world. It's not even the end of a life. Yeah, things change and you learn to navigate differently, but I've had quite a few worse things happen to me than psychosis. That's not to say it's not scary sometimes, of course, but it does become manageable over time if you make an effort. And yes, recreational drugs can still be part of a person's life when they have a psychotic disorder. I would just make sure to have as much "safety netting" set up around you - a support system of loved ones, enough medication that there's no danger of running out should you become incapacitated briefly, self-care strategies that work for you, etc.
OP, should you return, I hope you're well and that symptoms have indeed been kept at bay. I would like to hear how you're getting on with meds and recreational drugs. Take care.