trying to get hot air balloon to spawn a few yards in front of the player and not on top of player and killing them

I use
"cmd":[
"spawn hotairballoon \"$player.x $player.y $player.z\""

to spawn the balloon at the player but it is to close and kills the player sometimes 
tried this 
"cmd":[
"spawn hotairballoon \"$player.x $player.y+5 $player.z\""
and I don't see the balloon anywhere

The plugin uses what you type here and puts it int the console to execute.

I'm trying to adjust to spawn in front of player and not on top of player but Don't know the right syntax