Arching you bag is better for drive as well and creates a more stable base. Flat DB is a safer alternative I think. The weight travels in a less fixed plain and you can dump the weights ao less need for a spotter. It carrys over well to bench press strength as well in my experience.
will try the arch
Fair enough, learn to bench with a slight arch then, make sure your elbows are tucked. If you use an arch your chest is higher up and means a higher factor of safety when relying on safety bars, set the safety bars just above neck level and you should be fine.