Question to STRING FIT Contribute

Hi folks!

I have troubles with 3 FIT contributions as strings to the summary page:

If I declare "count" = stringLength, I get the error:
Error: System Error Details: setData string too long for allocated space

            myebikeenergyField = createField("ebikeenergy", ebikeenergyID,  FitContributor.DATA_TYPE_STRING, {:mesgType=>FitContributor.MESG_TYPE_SESSION, :count => 4} );     // l=4
            if ( myebikeenergyField != null ) {
                ebikeEnergy = 99.9f;
                myebikeenergyField.setData(ebikeEnergy.format("%.1f"));
            }    

            myriderenergyField = createField("riderenergy", riderenergyID,  FitContributor.DATA_TYPE_STRING, {:mesgType=>FitContributor.MESG_TYPE_SESSION, :count => 4} );  // l=4
            if ( myriderenergyField != null ) {
                riderEnergy = 99.9f;
                myriderenergyField.setData(riderEnergy.format("%.1f"));
            } 

            myprozenergyField = createField("prozenergy", prozenergyID,  FitContributor.DATA_TYPE_STRING, {:mesgType=>FitContributor.MESG_TYPE_SESSION, :count => 7} );   // l=7 
            if ( myprozenergyField != null ) {
                prozEnergy = "50 / 50";
                myprozenergyField.setData(prozEnergy);
            }    

If I enlarge "count" by stringlength plus 2, it compiles but on the real device (EDGE 1040) crashes sometimes (most times not...).

If I enlarge "count" by a large (secure) amount "count => 15" I'll get another error:
Error: Out Of Memory Error Details: New Field out of memory for FIT data

Why can 3 strings - each 15 characters - be too long for the memory...?

It seems to be a Tightrope walk between "too small" and "too large".

Does there exist any description of using strings in fit contribute?

(PS: if you ask: why using strings for the first 2 contributes? They are floats! Answer: there is a bug in Garmin Connect Web which ignores XML"precision=1" and it's rubbish to show 3 decimals on a value like Wh/km)