Right, you need to procure a shell that is large enough to fit over a minimum of layers: base, mid(soft shell) and insulation. Therefore, when wearing the shell by itself, or with only the base layer, it will be a tad baggy. You don't want a jacket that is too restrictive as, this will create problems with versatility and movement while climbing or another type of ascent. Better a little too big, than a little small.
Also, it depends on what kind of climb you are doing? If you are in a position of only needing it to go over one layer, you might be able to buy a tighter fit.
