Uh I've never done a solo 401k but I think the method you're proposing is going to cause some logistical problems (assuming you're making traditional contributions). If you had a 401k from some megacorp, then any traditional 401k contribution is deducted from your wages on your W-2. As in, if you earn $98k and you contribute $80k, megacorp reports $80k of wages on your W-2.
If you do it the way you just described, you're going to end up with say $80k of wages on your W-2, despite earning $80k and making $18k in traditional 401k contributions. And as far as I am aware, there is no way to report 401k contributions on your tax returns (somebody correct me if I am wrong on this - maybe you can do this on schedule C?)