Ok.
So we're basically talking about how much after tax $$ we can tap off our income stream to put into our B-fund before we hit limits that stop company contributions. This, if I'm not mistaken, is just another investment vehicle at that point (since the money is already taxed and future withdrawals receive no special tax treatment).

I like the B-fund and I max out my pre-tax contributions but, personally I prefer to diversify my after tax investment vehicles. I also believe there are better ones out there. YMMV.