The 6 Second Mount is a great option no permanent modifications to the gun keeps the RDS off the slide so it won't get beat to death eventually and has the added bonus if you use a pistol light with a laser you are less likely to lose the zero on the laser to do frame flex from temperature shift.
As for the Vortex venom it's one of the less durable red dots for mounting on the slide the Kings for that application are the RMR, Micro T aim points and the new Delta Point Pro but even these 3 will eventually die mounting on the slide in parts a great amount of force on the optic. I've seen some venoms last about 3.5k rounds before dyin and having to be sent in for warranty which is not an issue with Vortex but it also in my experience has never been an issue with Trijicon, Aimpoint or Leupold.