Do you know, that… ?

Sheet formed by the steps of Lofted does not cross the circle. Unfortunately, the upper and lower edges also are represented by the splines. Thus, as shown in diameter e.g.. w 1/3 the height of the sheet (or anywhere)?

Just create a curve intersection. The curve formed after selecting the wall plane of the sheet and inserted in the appropriate place.

Next insert point on the resulting spline. note, that created a three-dimensional sketch is a sketch.

The next step will replace the spline construction and intercede Circle by circuit based on the inserted point, and two points of the spline.

I intercede dimension circle and ready. If, after you insert a sketch dimension to redefine, Replace dependent on the size.