What is the trick? Everytime I slide the basepad on it pops off as I squeeze the sides to get past the tabs. I have the insert installed in the basepad first, is this the correct method? I also tried placing the insert over the spring end first, depressing the spring and insert while sliding the basepad on. This allows the basepad to slide past the tabs. But I can't get the insert to seat in the bottom of the basepad this way. What am I doing wrong???