Due to manufacturing tolerances and you varied oil dip stick life, it is recomended that you place a piece of scotch tape over the dip stick area and temporarity fit it in place and try to insert the dipstick into the pan. This will mark the scotch tape.

I used this method to arrive at my location.

You will want to measure 6 7/8" from the inner wall of the pan.

3/4" off the lower inner pan wall.

That is approx. the center of the dip stick travel path. I then drew in a 1/2" diameter circle.

I removed the spring nut before I contined so it would not be damaged.

I reinstalled 3 or 4 of the tray bolt to hold it securely in place while I operated the rotary tool. Be sure to use proper safety glasses and rubber gloves as the sharp metal bits from the pan like to stick in your skin!

I started with a 1/16" drill bit to spot the center and as I stepped up to larger size, it went beyong the edge of the lip on the lower structure. I then moved onto using burr tool with my rotary tool (dremel or equivalent).

I used the 1/2" circle outline as my guide. I marked my surfaces with whiteout since it was easy to see.

At this point I ran a polishing bit thru the edges to take down in sharp edges for safety.

I reinstalled the spring nut and bolted the tray down.