I had the same problem with poor scores on the slow fire. I am not sure you are still looking for advice?? I was able to shoot the timed and rapid in the low to mid 90's. What I did was set up like I was going to shoot a rapid fire for a slow fire. It is all in your head. So I picked up my pistol like I would for a rapid fire and then I made my shot and set the gun down and looked through my scope. I did this for each round and my scores went up from 87 on slow fore to 90 to 95.
This worked for me. It is all in the head....