Coming back to this after we just finished a new seat frame job on 980 MPa DP steel. Few things I learned the hard way that might save you some tooling.
Edge cracking on HSS seat frames is almost always a sheared-edge problem, not a forming-speed problem. We were blaming our motion profile for months until we started measuring the sheared edge condition on our blanks. Anything over 15% rollover on 980 MPa and you're going to crack on tight radii. We switched to a 2-stage blank with laser-cut critical edges and the cracking disappeared — even at 80mm/s forming speed instead of 60.
The other thing nobody talks about: die temperature management. On a 25 SPM seat frame job, the die surface hits 55-65°C after about 200 cycles. That changes your friction coefficient enough to shift the draw-in by 0.3-0.5mm, which on a tight seat frame geometry means your trim line wanders. We added thermocouple monitoring on the draw ring and punch face, and adjust the blank holder force -2% per 10°C rise above ambient. Sounds fussy but our Cpk went from 1.1 to 1.6 on the critical flange dimension.
For the motion profile — I'd push the dwell longer than 80ms on 980 MPa. We're running 150ms and the springback reduction is significant. The cycle time hit is minimal because you make it up on the return stroke. Our total cycle is still 2.4s at 25 SPM with the longer dwell.