Here is a picture of a box I made to hold my front fork in the
trailer.  It is pretty simple and works really well.  You can insert the
wheel without having to go to the front of the trailer.  Be sure to use
carriage bolts to attach it to the floor and not deck screws (I learned
that one the hard way). There is very little, if any, movement of the front fork.

Ratchet straps attached to the back axles at the axle housing pull the ppc toward the
rear. Note the braided nylon rope loops prevent wear on the axle.