I don't know about all models, but on an '04 Softail, ya gotta pull the outer primary cover. The spring will not fit through the derby hole. Just close enough to drive ya nuts tryin'. It ain't a major problem, even takin' off the cover.
It is possible on a TC touring bike, as I have done it before. However i do not recomend doing it as it very tight and a hammer is needed with the s/e spring. The o.e. one comes out rather easily though. Now when i do them i take my time, take the cover off, inspect the clutch, chain adjustment, and the comp nut. Then put it all back together with a new gasket. Now you have the confidence to know it is done correctly.....hope this helps