RB106 Phantoms and the disputed cost of carrier modifications

What if the British F-4K and F-4M Phantoms used the proposed high-thrust Rolls-Royce RB106 turbojet?

The installation needs airframe work; extra weight reduces some benefits, but the extent of that penalty is disputed, and Spey relight capability offers a separate operational advantage.

An RB106 installation would require airframe modifications. Fleet initially argues that the weight and other concessions needed for British carrier operations would absorb the extra power, leaving performance comparable to American Phantoms. Foxo challenges that assessment, and another response accepts a weight penalty while disputing its size. Fleet then qualifies the claim: the aircraft could still improve, although the gain would be smaller than the increase in engine power suggests. Better Spey relight capability is also identified as useful if an engine stops after leaving the carrier. No shared numerical performance comparison is established.