I bought a $140 chock on Ebay for my bike trailer.(Don't know the brand) I built a swivel wheel trailer last month and bought a $59 Harbor freight one for that. I like the Harbor freight one better. It's good quality and HD. It will work well with your Harley. I put all 4 bolts through the floor with mine but do like the "take out" idea.
I have the rail tracks in mine and with a screw every 2" they aren't going anywhere. I think your D rings will work if you use a locking chock because it's not going anywhere and the straps are to keep the rear from going sideways.