I´m not 100% sure for this, but i took a quick look at the schematic... Of course, the chip itself is rated for 85V Vin, but i believe, the capacitors (C10 to C17 ?) arent´t able to handle more than 50V on the IHM03A1. Another guess is the possibility, that a voltage flashover occurs due to the circuit board design.
So to be on the safe side, i wouldn´t exeed the rated 50V on the IHM03A1 ;)
/Charly
p.s.: Once i ran the ihm03a1 board with Vin at 48V, motor in current mode at 3A rms. After one year of regular use, it´s still alive ;) With another motor, also 8A rms at Vin of 24V wasn´t a problem (but this was just a quick check, if it a) works and b) to check heat dissipation of the shunts...) :)