Unlike most tail bumpers, the FJ-4's was very narrow - basically a blade - and not retractable. There was a fixed guard in front of the bumper, which could pivot to absorb the shock of a tail-low touchdown. There was almost certainly a damper involved, since the bumper is always extended except on museum examples (see second picture) where the damper is missing or inoperative. There was a tie-down hole in the bumper.
23 January 2017: Some notes on and pictures of the 1/72 Emhar kit can be found here:
October 2016: Updated to revise the horizontal tail discussion and correct other details.
In the process of preparing an information package requested by a kit maker, I revisited a question raised several years ago, the size and shape of the horizontal stabilizer. The problem is a fundamental inconsistency among the drawings and data available to me, which include the excellent North American FJ-4 four-view drawings, the FJ-4/4B Standard Aircraft Characteristics (SAC) charts, two NACA spin tunnel test reports, and a couple of measurements of an actual FJ-4B stabilizer by Jim Robbins. Thanks to FJ-4 maintenance manual data provided by Frank Truchi, a volunteer at the National Naval Aviation Museum, I can confirm that the NAA drawing of the horizontal tail is correct except for the span and the location of the elevator.
Note that the FJ-4 empennage was subjected to development changes.
In the process of reviewing the documentation I have, I discovered a detail that I wasn't aware of before. The major change between the FJ-3 and the FJ-4 was the wing. The new one provided more area to lift more weight, much of which was fuel. The knock on the FJ-3 was that performance suffered when it was carrying external tanks and endurance suffered when it was not. As a result, the FJ-4 was to have the same internal fuel capacity when clean (no external tanks) as the FJ-3 configured with external tanks. The ailerons were also to be moved inboard to avoid weight that would otherwise have been needed to stiffen the wing torsionally, which didn't leave much trailing edge available for flaps. As a result, the FJ-4 had narrow-chord leading edge flaps to further increase camber and a panel hinged to the bottom of the flap to scoop air into the slot between the leading edge of the flap and the aft spar of the wing.
One tidbit about the FJ-3 versus the FJ-4 that I'd forgotten was the increase in tread. This didn't result from the main landing gear struts being relocated more outboard: the wheels were simply located on the outboard side of the strut rather than the inboard side.
The FJ-4 had excellent handling qualities, eliminated the FJ-2/3's gunnery inaccuracy that resulted from the excessive downward angle of their cannon, and was almost certainly one of the best jet fighters from a performance and maneuverability standpoint that didn't have an afterburner. Unfortunately, fighters with afterburners had an innate interception and air-to-air combat advantage so the Navy gave all the FJ-4s to the Marine Corps, which was happy to have them until Vought produced more F8U Crusaders than the Navy needed.
However, that wasn't the end of the FJ-4. The Bureau of Aeronautics decided that Douglas' Ed Heinemann wasn't paying proper attention to its concerns about the A4D Skyhawk program so it contracted with North American for an attack variant of the FJ-4.
It turns out that they were on the upper surface of the flaps as shown in the SAC drawing above. Note the open spoiler on this FJ-4B's damaged flap.
For an FJ-4B configuration with the left-hand cannon removed, see: http://tailspintopics.blogspot.com/2012/03/modelers-guide-to-sabre-fury.html
For some detail under the canopy see http://tailhooktopics.blogspot.com/2012/12/fj-4-detail-under-canopy.html. Note that the FJ-4B was in service long enough to be retrofitted with the Martin-Baker ejection seat.
For an excellent set of annotated photos with configuration and other information, see this Phil Friddell post: http://tailhooktopics.blogspot.com/2012/12/fj-4-detail-under-canopy.html
For a summary of all the different FJ Furies, see http://tailspintopics.blogspot.com/2009/10/fj-fury.html
And, of course, there's great information and drawings in Steve Ginter's FJ-4/4B monograph, Naval Fighters Number Twenty Five, which is regrettably out of print.