No, it's not possible with /echo -i, however, have you tried $wrap with the optional [word] parameter? Look up $wrap in the help file. Examples:

//echo -a $wrap($str(wholeword $+ $chr(32),50),fixedsys,-9,500,0,1)

//echo -a $wrap($str(wholeword $+ $chr(32),50),fixedsys,-9,500,1,1)