Let's see if I understand this correctly since I do have a P-19MX w/ spin ...

The bridle tang is shaped like a 'T' ... mounted upside down w/ the stem of the 'T' upward ... and the top of the 'T' is mounted for-aft just under the deck -lip/gunwale and "glassed" in place ...

Is this correct ...???

It is much easier to work thro a larger hole ... and is just as much work to repair properly then a smaller hole ...

you can use a hole saw but expensive to get one that makes a large enough hole ... I just cut square hole using a jig-saw set at 30* bevel ... like carving a pumpkin ... install a lip and then replace piece cut-out and re-skin the outside ... your most important finishing tool will be a wooden sanding block so as to have a 'fair' patch w/o ripples ... and the palm of your hand, cause you need to feel the ripples ... and spend the time hand-sanding between changing sandpaper grits ...

Harry Murphey
P-19MX w/ spin
H18Mag