If I was to tie down the front, I would strap to the lower trees.
This is a good idea.
I ask you to think about this: How bad would you feel to have the cycle come loose and go over the side?
I've had this happen to me (not to my 14R).
The *single* strap (one on each side) had dry rot, and I did not know it, it looked fine.
Going around a curve, and hit a bump while in the turn. Physics dictates an immediate, enormous increase in load to that strap. Snap! Over the side it went. I dragged it about 20 yards before I could get stopped safely.
That was a very expensive lesson, one I'm passing on to you, gratis.
*My* straps are two per side, forward, to different mount points on the trailer (I will not tie-in two straps to the same mount point now). One in the back to prevent wheel hop, or the bike going "over the top".
... while using a good wheel chock, like you have.
It takes a few extra minutes to sort it out, each time. I also had to drill into the trailer sdge to obtain additional mount points.
I no longer stare out my rearview in apprehension.
2012 Blue ZX-14R, Cox rad guard, Skene Design P3 Lighting, Knight Design 1" lowering pegs, Grip Puppies, BrakeAway, Cortech Sport tailbag, GSG MotoTech Frame sliders, Stebel Compact horn.