Import .fit from third software in my forerunner activity

Hello,

During hometrainer session, I use my Forerunner with indoor ride and third application. The associated .fit files of my application contains all data. Obviously, my forerunner don't have any elevation values.

I discover the SDK environnement. I've convert my .fit file into .csv. I compare this one with my Garmin recorded activity.

Like a newbie, I copy/paste 2 lines which contains Garmin Forerunner information into .csv with all my information.

CSV to fit fails :

FIT CSV Tool - Protocol 2.0 Profile 21,94 Release
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1
        at java.util.ArrayList.elementData(Unknown Source)
        at java.util.ArrayList.get(Unknown Source)
        at com.garmin.fit.csv.CSVReader.readCSV(CSVReader.java:104)
        at com.garmin.fit.csv.CSVReader.read(CSVReader.java:58)
        at com.garmin.fit.csv.CSVTool.run(CSVTool.java:296)
        at com.garmin.fit.csv.CSVTool.main(CSVTool.java:419)

I suppose to miss something...

So, is it possible to do what I try to do ? If yes, how to do it ?

Thanks a lot.