I'm not an expert, but my understanding is that modifying the ICE mounts to eliminate vibrations is similar to a combination of balancing wheels and tuning a guitar. You wouldn't really notice the difference in the final product unless you knew what to look for.
I'm not sure what you mean by modifying the mounts, but from the 2026 Technical Regulations:
5.6.17 Engine (ICE) mountings may only comprise six M12 studs for connection to the survival cell
and either four or six M12 studs for connection to the gearbox case. These studs may be
fitted on the survival cell, power unit or gearbox case, their installed end must be M12 and
their free end may be a different diameter.The six mounting faces of the studs for connection to the survival cell must lie at [XPU, Y,Z]=[0, ±270, 25], [0, ±360, 270] and [0, ±190, 440]. All six of these studs must be used.
The four mounting faces of the studs for connection to the gearbox case must lie at [XPU, Y,
Z]=[480, ±125, 25] and [480, ±265, 360]. All four of these studs must be used. Optionally, an
additional two studs may be used, provided their coordinates are at [XPU, Y, Z]= [480, ±150,
140].
A tolerance of +/- 0.2mm will be permitted on all of the above dimensions, all dimensions
refer to the centre of the studs. All dimensions in this Article refer to studs fitted
symmetrically about the car centre plane.