Wildcat MK2 Tuning

I have a Wildcat 2 that I am trying to make a slug shooter out of it. I have the dual high flow port with high flow pellet probe installed. I have a Huma regulator set at 150 measured by guage. I just installed an 11 gram hammer. As far as I can tell, I can not keep my pellet probe opening aligned with the dual port. As soon as I cycle a couple pellets the velocity drops. If I reset my pellet probe in as far as I can get it, the velocity goes up. Cycling pellets seems to cause the pellet probe to slide back and out of alignment. I am baffled as to stopping that. Any thoughts welcome.
 
Those 2 screws on the cocking rod are horrible at staying tight. Augie (bigragu) sent me some stainless torx screws to replace mine (for doing the same thing), and it hasn’t lost velocity yet. I was ready to give up on mine, but now it’s perfect. 


btw, mine is setup with enough power to throw knockout slugs in .25 to 930fps if your looking for confirmation they can have enough power. 
 
Not sure if this will help or not, but I do know the stock MK to Wildcat has a 1:37 twist barrel. These do not do well with slugs. If you can or if you haven’t done so already go with a superior twist 1:22, or I think the new ones are 1:24. This will shoot your slugs much better and allow you to lower your reg and shoot slugs a little slower but still keeping your accuracy. You may know this info already.