I use my vest when my port is accessed. All I do is loosen that side of the shoulder strap and put in a balled up sock or something else to stabilize the needle if it sticks out far (like a 1 inch needle does.) I don't have any trouble with the 3/4 inch needle.
When I don't use my vest (for other reasons, I used the Acapella, the Quake, or I have my husband aminister CPT.