Treebeard- Why would I have to get rid of one of the trunks? I have seen a few triple trunk maples. Peter Adams highlights one in his book (Tree #11 in Chapter five)...
Rich, sorry it took me so long to answer your question. (You may have found the answer by now.)
As a pretty consistent rule, if there are more than two leads (branches or trunks) arising from the same point, you're going to get a reverse taper there sooner or later. Two branches leaving a trunk at the same point, for a total of three; a trunk that divides into three or more secondary trunks -- anywhere you have that situation, a reverse taper is very likely. Some species are more prone to it than others.
In that picture in Adams' book, do the trunks all arise from a common root? Or does the trunk divide somewhere above the nebari, as yours does?
I have a nice
Ficus neriifolia reg. that I got from Bob Eskeitz. Its trunk divided into three about 3 inches above the nebari, and when I got it a reverse taper was becoming visible at that point. (It had enough else going for it that I bought it anyway.) I immediately removed one of the trunks, after deciding where the front would be. I'm developing a low back branch on one of the remaining trunks to restore the tree's visual depth. I plan to train aerial roots down to hide the "egg."
f I hadn't taken one trunk off, I would have a serious bulge there by now.
It's your tree, and you can go for a triple-trunk if you choose. I'm just saying it's a calculated risk, and one that, in my experience and observation, the human usually loses.