Looks like you already found the solution. The pressure plate is a nice add on to avoid using the clip.

Just a little information explaining the ATC. There are a couple things you have to do differently with an ATC than with a manual change.
The first is to get the length of each bit in the tool holders this is done with CN,72 "Zero Tools in Rack". This routine only needs to be run on the bit that has changed. If you are first setting up then CN,72 would have to run through all the bits. Then if you replace a bit in a tool holder only that tool number would have to touch off the fixed plate with a CN,72. This routine is used to record the length of bit in the tool holder for when you make an automatic tool change the Z zero is updated for the new length.
The C3 is different with an ATC as it will home/zero all 3 axis, ZY and Z. The Z zero will have the Zero location set to the location from running CN,73 "Get Plate Offset". Typically this would be the top of your spoil board. Then everytime your run C3 the Z zero will be to the top of the spoil board. With the CN,72 and CN,73 set you really should never need to use the standard touch off plate C2.