I am mocking around in the pant's simulation source file and I noticed a shape key that controls the waist line is named "shrinkwrap". This got me to wondering if I could use the shrinkwrap modifier to set the pin vertexes position but I can not figure out how to get around the "can not apply modifiers to object with shape keys". Do you have a solution or was the vertex naming just a coincidence? Thanks.
If I recall correctly, you're right that I used a shrinkwrap modifier for specific vertices around the waist (using another vertex group to isolate said waist vertices). Once I got the effect I liked, I applied the shrinkwrap modifier as a shapekey. That option auto-named the vertex group.
Can you provide a download like to your .blend file so I can take a look as to why you can't apply as a shapekey?