The hovering sombrero gives bonus stats equal to min(ML/4*(0.1+0.005*weight), 100). Mafia uses max instead of min, so it calculates a stat gain of 100 for low-level monsters. Line 2370-2371 of Modifiers.java should read:
Code:
this.add( Modifiers.EXPERIENCE, Math.min( factor * ( Modifiers.currentML / 4 ) *
( 0.1 + 0.005 * effective ), maxStats ), "Sombrero" );