I'm trying to add centrelines to a pipe frame by drawing them in. This is tedious and as soon as the model changes slightly all of the sketch references become unsolved. This make the whole drawing process painfully slow.

I've tried other methods. The first was to add centre lines as annotations. The problem here is that I need arc lengths along the pipe and this is difficult to achieve using annotation centrelines. In addition it is hard not possible to get intersection points of the annotation lines.

The other method is to highlight a model sketch and convert this to the drawing. Problem here is that that certain views like details won't allow you to select those model sketches for the conversion.

Any other suggestions?