The Curt Trailer Hitch Receiver # C11145 has a bolt hole separation of 5-7/8" on center. I have included a picture for you as well for this measurement.
I have also linked the installation instructions below. view full answer...
The 4-Leaf Slipper Spring w/ Radius End for 2,000-lb Trailer Axles # e69SR should be compressed ~2" under a 1,000 lb load which would make the "F" measurement ~1 3/4" with the 1,000 lb load. This is based on a formula to find spring compression since we don't actually have that info at hand so take it with a grain of salt. view full answer...