Will it have a large impact on fermentation if I do so now vs. later?
Not really, and by waiting, you could adjust to taste.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk
I didn't get a chance to make it to LHBS to pick up extra ingredients needed, and it's a bit late now, so I'm going to let this one ferment out.
My fermentation control also did not work as well as I'd have hoped. I pitched the yeast way too warm (about 85F) and it cooled steadily over the next 24 hours to about 65, then I tried to tweak it a bit to hit my target of 62, but overshot and it hovered around 59 overnight. Now it's close to 62 again.
So I will call this yet another highly experimental batch, and I'll leave it at that.