Actually, the F-4 was an easy jet to fly in formation - very stable while on the wing. Those bent - up wingtips seemed to give her a lot of stability in the roll & pitch axes which aided in remaining in close fingertip formation. Ditto for staying on the tanker boom during air refueling. I don't recall having 40# of downstick force when I flew them. Maybe that was after I flew them - I don't know.
The jet was so responsive in the pitch mode that, on takeoff, we held the stick full aft (nose up) until about 150 knots then gradually moved the stick to neutral and slightly aft to rotate the nose to the takeoff/climb attitude. This was done to keep from dragging the stabilator on the runway and grinding about a foot of it off as happened in the early years of flying the jet. At full aileron deflection, she'd snap roll at 720 degrees per second (2 complete turns about the horizontal axis) which was enough to completely disorient the pilot if he tried it. We didn't like doing that and used that maneuver only as a demonstration when a pilot was transitioning to the Phantom. The aircraft needed 10,000 feet from the start altitude to do a symmetrical vertical loop if done properly.
When I came back from SEA, I did a 2-year stint at Nellis AFB, NV as an instructor in the USAF Fighter Weapons School as an Aggressor Pilot in the T-38A & the F-5A where we flew as "enemy" fighter pilots against active duty USAF, USAFR and ANG pilots in whatever jets their units were flying at the time. Most of the pilots at the school were recent SEA returnees who flew the F-4, F-105 and the F-100 in combat. We taught those guys a lot about how to not get shot down from what we learned in actual air-to-air combat over North Vietnam, Laos, Thailand and Cambodia.
Exciting times those were, indeed!