fitField - how to determine its column's position among the standard (SPORT_GENERIC) lap fields?

I have defined a fitField in my resources file like this:

<fitField id="101" displayInChart="false" sortOrder = "2" displayInActivityLaps="true" dataLabel="@Strings.IntervalLabel" unitLabel="@Strings.IntervalUnitLabel"/>

Then, in my code I have this:

lapField = session.createField("Interval", 101, FitContributor.DATA_TYPE_STRING, {:count => 5, :mesgType => FitContributor.MESG_TYPE_LAP});

My expectation was that my field's column will appear as the second column (sortOrder = "2") in the lap output in my Activity record in Connect Mobile, after the 'Lap' column (which is the first column).

Instead, the column for my added fitField appears as the last column.

My Activity is of type SPORT_GENERIC.

Does anyone know how to let my new fitField to appear as the second column, right after the 'Lap' column?