At the risk of sounding like my younger son, "but why?". I definitely like the look of a double trunk with one trunk being more dominant, but is that a rule of bonsai aesthetics (like, stay away from inverse taper)?but a twin trunk with both trunks of the same size isn't the best.
I have been searching for pics of twin trunks with two similarly sized trunks and this is what I found. (The last pic is a split trunk, but I think it conveys the point as well).
I will leave this tree as the last layer, as I appear to be pretty indecisive.