I was doing the math on our balance of 160k, at 110k is where the inflection point occurs on a 30yr. That seems to me the math is front loaded, maybe I’m wrong.

Calculate for each month: (interest paid) / (unpaid principal).

E.g., for a $100K, 30 year, 5% mortgage

Month #1 = $416.67 / $100,000 = 0.0041667

Month #2 = $416.17 / $99,879.85 = 0.0041667

...

Month #120 = $339.75 / $81,539.35 = 0.0041667

...etc.

0.0041667 = 5%/12. In other words, one pays exactly the same interest rate for each month of the mortgage. One hears the phrase "front loaded" but it's not a good description of what is actually happening.

The oft-debated issue of "pay mortgage or invest" is another question. ;)