Yes, both boards may have a similar width but on the 158 the back foot is more over the tail where it is wider. On the 170 the stance is closer to the narrower part of the board.
Are td3's higher than td2? .
As to selling it, my intent is to see if I could ride the board, but if it not going to work for me I would rather sell it before it touches snow. That's why I asked here if lifts would work. No big conspiracy