I did line one the notch , but the wouldn't stick or stay , I felt resistance pushing back, I did take off the bottom to check it out, and the plastic lining ripped cause I tried to force it inYou just need to line up the notch, no need to remove the bottom casing. I added a tiny bit of adhesive before installing the feet to help prevent them from falling off.
This doesn't look like the ones I haveMacBook Pro: Bottom case foot replacement DIY instructions
although some replacement kits boast of their 'special glue & sticky pads' making bottom case removal unnecessary.
there is a black plastic covering the inside corners , would I have to peel that off?They're attached from within the case. So you'll have to take off the back first.
I have a picture of the feet I bought attache din the first comment , the inner circle is smaller than the ones in the linkWhat do yours look like? They should just pop in more or less, secured by the glue/tension fitting.