187 had slight mods to house longer projectiles and a more powerful engine, but the biggest change is that the front hull adopts a similar layout to the Leopard 2: a very sloped roof plate that houses the driver's hatch so this weakened zone is no longer exposed, and a less sloped (50-70°) plate. This solution also increased the available thickness to install more steel and NERA.Do you have any information about how the hull geometry varied from the T-64/72/80 series compared to something like the Object 187?
That's the geometry the Object 772, 775 and 480 also used to partially or fully eliminate the driver's hatch weakpoint.
The other solution used in the Yugoslavian Vihor, the Soviet Object 172-2M and the Object 775 (alternative) was to increase the slope of the single T-64-like plate even further so the hatch basically fits seamlessly or at least the weakened zone is much smaller. But this solution requires either reducing the roof area in front of the turret, lengthening the hull front or increasing the size of the lower frontal plate as a tradeoff.