It's not really trigger slap, because the trigger linkage is completely disengaged from the operationg parts as soon as the trigger bar releases the hammer. There is no longer a direct mechanical connection like there is in the AK.
What happens to many folks is the front of the trigger guard beats the snot out of their finger during recoil. Try to consciously maintain backward trigger pressure to keep your finger from staying in one place while the gun goes backward somewhere else.
And I second the suggestion to shorten & round off the tip of the trigger a little.
Also remove & smooth the sharp mold parting line in the center of the guard.
Again, during recoil, the fleshy part of your finger is getting pinched between the sharp end of the trigger & the sharp seam in the trigger guard.
Gun goes up & back - finger trys to stay where it was.
It ends up between the sharp tip of the trigger & the guard.
rcmodel