OK, I have a part that I have designed to be cast. It is a square flange that has a cylindrical shaped extrusion that allows me to have a 3" FNPT area in the middle.

The base of the cylinder has a 1/4" fillet all around where it connects to the base. The end of the cylinder has a 1/8" fillet, all the way around, in order to assist with mold release (avoids sharp corners). The cylinder has a 1° draft (inward) applied from the base to the end. (see image below).

Being that there are fillets at the base and at the end, I do not have an adequate way to indicate, to the mold maker, a reference diameter of the cylinder - which would be the end-edge that I applied the fillet to on the part. My current work around is to sketch points to imitate the intersecting locations of the tapered cylinder wall and the end of the cylinder and then dimension the points. If you look closely, you can see the faded-out points in the image.

Is there an easier way to do this? Like, is there a way that the dimension will "automatically" grab the non-existent, or no-longer-shown, edge that the fillet was applied to?