Wadcutter for FX Impact .177

Has anyone found a .177 wadcutter that the FX Impact likes? If so at what velocity?

The best I've found from my testing is the RWS Supermag and even then I've only been able to get my groups down to 1.5 cm at 20 meters. (For comparison JSB Exact 10.34 are giving me one hole groups at that range...) Heck, my JSB Exact groups at 70 meters are roughly the same as the RWS Supermag at 20 meters! 

I really like using wadcutters for small game at close ranges but they aren't much good if I can't put the pellet EXACTLY where it needs to be... To be fair I haven't yet tried the "redneck hollowpoint" (Backwards pellet) but I've tried quite a few different wadcutters at various velocities, all with mediocre accuracy results at best. 

Could it be that the Impact just hates wadcutters? 
 
At least I'm not the only one with Smooth Twist that doesn't like wadcutters... 

Polymags- Too rich for my blood... Plus the length doesn't always play nice with the Impact magazine from what I've heard. 

H&N Crow Magnums- I'll have to give them a try...

I was afraid that the ST barrel and wadcutters just are not compatible, and the more I test the more I tend to lean that way. It's a bummer for sure, but at least this way I've got an excuse to get another PCP for short range hunting with wadcutters... ;) Of course I could just suck it up and use the JSB Exact 10.34 and deal with the "over penetration" issue. 

Cheers