1.6 vs 1.5 rocker will not change the seat duration, but will change the duration at 0.050"
(and the duration at every other lift point)

Lift increase with 1.6 vs 1.5 = (1.6/1.5)= 1.067

So if you've got a camshaft with 0.484"lift on a 1.5 rocker, it will become 0.484x1.067=0.516" lift with the 1.6 rocker

Seat duration = 0.000" lift
Not even a 1.9 rocker will change that.
0.000x1.9 is still zero.

If you look at the duration at 0.050" that does change with the 1.6 rocker, cause the 1.6 rocker increases lift.
0.050"x1.067=0.053"
So what the duration the cam had at 0.050"becomes the duration at 0.053" with a 1.6 rocker.
And the duration at 0.046875" becomes the duration at 0.050"
(0.046875x1.067=0.050)

F.