We have checked the possible solutions and it seems that it is the d3 library restriction. We cannot align secondary axis labels with grid lines and still show round units on the secondary axis. Therefore it is not possible for our developer’s team to fix it.
Too bad. In highcharts it does match… http://www.highcharts.com/demo/combo-dual-axes
We do agree that such limitation from the d3 library is quite inconvenient. Nevertheless, we have added this task to our backlog and we will take this feature into account when discussing future Flexmonster improvements.