Joe - I hear you loud and clear on the peace of mind, however, there is still peace of mind knowing that you have 1.2 in other investments! I have a large cash balance (48k) which is way higher than 16.7% for me. I justified it knowing that I was making 4% interest at my bank. Recently, my BF opened a Vanguard account with 10k in VTSAX. We have only added $350 to it since and the balance is 10650 in one month. That's a great return and a clear cut winner to my 4% interest over time. Yes, the market may go down, but you have a sizable cushion. If you aren't willing to put it all in consider putting half. I just transferred 24k of mine to VTSAX and am very much still at peace knowing the other 24k is a one year emergency fund for me. Good luck!!
PS - I also agree with @PoF to pay off the mortgage and then see how things shake out.