Even at pH 5, 98% of the DMT is in salt form (and therefore water soluble) according to the
freebase percentage calculator, so you'll have a good enough pH in theory. But lowering the pH to 4 or even a bit lower so is not a bad idea because then you'll have 99.9+% of the DMT in water soluble form, but also because the low pH helps break down the cells and expose more of the DMT to the water. This is specially true if you have shredded bark as opposed to powdered.
So yeah ph 4.7 or whatever is just fine, but if you want, do get it a bit lower just in case.