I have a cci grip on my other cat but it does not have the bottom line threads. I know you can get block for the bottom line my brother inlaw has one on a alley cat with one on it.
this is what i got as a pic i mounted it to the section just befor the barrel with the "custom mounting kit". I have seen them under the barrel going forward and I have seen them vetical under like a for grip.
This works best for me becaus I am left handed and I reload from the right side of the marker and I can see were I have to reload becaus it is in my face. look in the ICD pic thread some other guys have pics up too. hope this helps
I would like to see a pic of the grip you have you can just pm me you dont have to post