Last link is just as strong as the first link. Chain length makes no difference
I also have a windjammer with the under mount coupler. On my propride hitch I use the last hole in the link bar
On his hitch you want the head tilt and chain length adjusted so the spring bars are about parallel to the frame when the front end is at unloaded height and a slight downward tilt on the head. You may need to add or remove washers adjusting tilt and then add or remove chain links or restore front axle weight.
With the under mount coupler you will need longer chains than a similar setup on a top mount coupler to get the bars parallel.
Linc
