In support of their Model 225 fighter design, an entry into the VFX program (eventually to become the F-14), McDonnell built a test rig mounted to an F-4 Phantom II. Their Model 225 carried the Phoenix missiles semi-submerged; missile ejection was carried out by pnematic “ramps” that, at full extension, served as doors to cover the holes left by the missiles. Thus the missiles were carried in an aerodynamically clean configuration, and left an aerodynamically clean surface behind them after they left. To prove out the concept, the centerline tank from an F-4 was modified to carry a single missile and the associated pneumatics and doors and such. Without the radar system used on the F-14, the F-4 would have been a poor carried for the Phoenix; this was simply a test program to demonstrate the missile ejection system. Sadly all the info I have on this comes from a brief writeup early in the process, and the two attached photos. I don’t know if any ejection tests were carried out.