I actually find setting of the shoulder pads to be quite tricky, at least with the drafts I use for my own garments. I have found it can depend on shoulder seam slope - as well as the length of the shoulder seam (ie. narrow vs. broad shoulders) - which serve to define the final angle of the armscye in relation to the shoulder. For me, the solution is to set the shoulder pad so that it corresponds to the armscye at the front and back shoulder pad tips, and then to rotate it outwards until it fits snugly inside the shoulder region. This invariably results in excess pad which protrudes at the top of the armscye, and this needs to be trimmed off.
So, to answer your question: in my opinion it is important to have the shoulder pad extend completely to the seam along its entire length, but the way of achieving this is to ensure it fits correctly with excess and then trim it to shape.
It's supposed to align with the edge to create a continuous line. Sometimes it requires playing with the front and back edges. Usually, I start by aligning the center notch. More than once I've confused the front and back sides. This may sound crazy, but because the shoulder blade is angular, I always want to put the fuller side of the pad facing the back instead of the narrower side. It's especially bad if the shoulder pad has a front and back that are similar in shape -- but maybe that's a low-quality pad.
If it's not possible to make it conform, you can take your pattern, place it on top of the shoulder pad, trace the outline, trim the pad, remove any excess wadding and stitch it closed by machine or hand. You can also make your own pads. Trace the shape, add seam allowances, cut out two in muslin, then take the wadding from the commercial pad or another source, add it, and sew it. There are videos online that demonstrate this.
It's also possible to make custom sleeve heads with strips of muslin on the bias.
I actually find setting of the shoulder pads to be quite tricky, at least with the drafts I use for my own garments. I have found it can depend on shoulder seam slope - as well as the length of the shoulder seam (ie. narrow vs. broad shoulders) - which serve to define the final angle of the armscye in relation to the shoulder. For me, the solution is to set the shoulder pad so that it corresponds to the armscye at the front and back shoulder pad tips, and then to rotate it outwards until it fits snugly inside the shoulder region. This invariably results in excess pad which protrudes at the top of the armscye, and this needs to be trimmed off.
So, to answer your question: in my opinion it is important to have the shoulder pad extend completely to the seam along its entire length, but the way of achieving this is to ensure it fits correctly with excess and then trim it to shape.
It's supposed to align with the edge to create a continuous line. Sometimes it requires playing with the front and back edges. Usually, I start by aligning the center notch. More than once I've confused the front and back sides. This may sound crazy, but because the shoulder blade is angular, I always want to put the fuller side of the pad facing the back instead of the narrower side. It's especially bad if the shoulder pad has a front and back that are similar in shape -- but maybe that's a low-quality pad.
If it's not possible to make it conform, you can take your pattern, place it on top of the shoulder pad, trace the outline, trim the pad, remove any excess wadding and stitch it closed by machine or hand. You can also make your own pads. Trace the shape, add seam allowances, cut out two in muslin, then take the wadding from the commercial pad or another source, add it, and sew it. There are videos online that demonstrate this.
It's also possible to make custom sleeve heads with strips of muslin on the bias.