I've only been growing this plant for a couple of months, and, tho it seems to be coming along well, I have no experience trimming the tops. Sorry.
But if I may piggyback on your thread, I have been having issues with the other end. Mine don't seem to be developing roots in the substrate. As such, they float easily. And the bottom end of the stem was soft.
So I trimmed the bottom portion and replanted, using weights. They seem to form roots readily a couple of inches above the substrate.