Just to illustrate the impact of the 16+ boost, the Spit V is now 17MPH faster than it was at 12+ boost. That means its only 1-2MPH slower than the Spit IX and 12-13MPH slower than the 109F-4, yet will turn circles around those two. The 109F-4 does not own the verticle against the Spit V anymore either, which used to be its main advantage. The F-4 is still better in the verticle, but not clearly superior like it was.
Squire and others have documented that the Spit V did use 16+ boost, it did, thats not at issue. What is at issue is where in the "operational life" of the Spit V was it cleared for 16+ boost? It was late in the operational use of the Spit V (after the introduction of the IX), and for the majority of its use (and for the time periods it is usually used in the CT) it was only cleared for 12+. In the MA it makes no difference because its enemies will not be limited to '42-'43 planes like in the CT. As it stands now, the Spit V is superior to the Spit IX in every respect except for the IX's ability to carry a droptank. Since the CT typically has fuel burn set well below the MA 2.0 setting it really makes the IX redundant.
I dont hate the Spit V, on the contrary its my main ride in the MA so I know it fairly well. Against its contemporary rivals, I feel that any other plane has three options against it, which are either run away, gang up on it, or die. IMO It is detrimental to CT gameplay with its current modeling.