From my experience it's best to use downers for the comedown.
I'm not talking about Heroin though, just benzos OR pharmaceutical opiates ( at a prescribed/or as close to a prescribed dose as possible).
I haven't tripped in decades, but I wouldn't take acid if I didn't know that I had something to help me with the comedown if I needed it, ( and when I say comedown, I mean it actually becomes something pleasant if planned correctly, you don't want to "knock" yourself out with taking something as strong as H or large doses of benzos, in fact I looked forward to that point and tried to postpone taking a downer for as long as possible, and it just added an extra 4-5 hours of bliss and clarity to my experience.
I have only positive memories from those days and absolutely no cravings or thoughts about acid (only when I am triggered by BL members questions, but it's the best advice I can give you).
Don't spoil something so special by adding the H to the mix.
Keep the H for another time if you really have to use it.
In fact I have a feeling that a good "trip" or acid experience (which it will be if you use your opiate tablets in a small dose when you feel you have had enough - oh man, the relief and extra chill time feeling like a king was sublime - will change your mindset about H in a positive way).
Be safe.