Any comment on the Cruel C51 or the Cruel Intent? I might be able to get a good deal on one of these. Is the Cruel Intent the same cover as the Primal Rage? Fusion Pearl Reactive.
I have the Primal Rage and it isn't the ball I though it would be either. Can't find the right surface and condition to use it on. When I go duller it is too early, not clean enough and not enough backend, but when I go shinier it skids too much in oil but still doesn't have the backend I thought it would have. This is from 4000 polished, to just knocking the shine off with a 4000 pad by hand.
When you get to the older Motiv equipment, you will find their covers weren't as strong as some of the bigger named manufacturers. The Cruel C51 had the Cruel core which maxed out the differential values allowed by USBC (0.060 diff, 0.030 int). This core was problematic for some if it wasn't drilled accurately for the bowler. The hybrid cover was strong, but not as strong as other strong pieces by other companies.
The Cruel Intent had a different core (Sinister) and was more along the lines of other asymmetrical cores from other manufacturers (0.053 diff, 0.018 int.). The introduction of the Fusion Pearl cover by Motiv was the first time their covers approached the performance of bigger names like Storm and EBI. Since then, their covers have gotten better.
Cruel Intent would probably be better suited for medium-heavy instead of true heavy, while the Cruel C51 would be better suited for medium in my mind (depending on drilling).
I see you have the Venom Shock and Covert Revolt. If you are looking for more movement downlane than your Covert Revolt (similar shape to your Venom Shock) then perhaps the Revolt Vengeance. The cover provides push through the heads and recovers better than the Covert Revolt. Overall strength will be similar to the Covert Revolt, but may appear stronger since the reaction is downlane instead of through the whole lane.
If you want even stronger, then the original Jackal could be an option. Coverstock provides push similar to the Vengeance, but overall will be stronger. Remember, the Covert core (Vanquish) is symmetrical and the Jackal core (Predator) is asymmetrical so the drilling of each will vary slightly.
Good luck!!
P.S. Does your Primal Rage have a balance hole yet? Perhaps strengthening the core with a hole to increase the dynamics will help prevent some of the over/under you are seeing. Another option is to use a lower grit under your polish to get something different. Something like 2000 with polish. And I don't recommend the Motiv Polish. Their cleaner is decent and their Scuff I feel is pretty good.