Having an ASP 12 I agree with this one little difference between a 12 and 15 ditto for 21/vs/25 have ASP 21 also, it comes into play with a little bigger engine example a 40 vs a 45 or 46 martin

There is always an exception my enyna CX11D is quite a bit stronger than my. OS10 diesel conversion it is BB engine (the enya)