I was able to solve this problem with Norm's help! Thank you again!!!
I redesigned my grips to be more durable. I've heard the backstrap cracking problem which has occured on some not precisely made guns. (There is 0.3 millimeter difference between the frame's two important points on those guns.)
The first change affected the backstrap. Here is a picture that shows the difference. The blue line is the old backstrap contour.

There is another change which I can not show on picture. I made the inside of the grips a bit wider so they will slide up easily.
More pictures to show the finished stocks. I think you can see the difference. They become wider (+1/8") than my original grips.


!!! Anyone who had difficulties mounting my grips, please let me know. (If the top edge stucked and you had to force to slide them to position) I'm ready to send a replacement set for you and for anyone want to change his/her existing 'Dennis' grips a better/safer one.
Have a nice day!
Dennis.