Buying a soft rubber "stress ball" and closing your thumb and fingers around it towards meeting each other in, say, sets of 10 will strengthen the cupped hand. And/or curl and straighten each finger against pressure from your R thumb.
Much of the comfort of the LH shape comes from the relative length of fingers which in turn partly comes from the squareness of the palm. Hold your hand up in front of you, close your fingers and look at your palm. If it slopes too much from the base of your index finger to the base of your pinkie this will pull your elbow down to maintain arched fingers.
If your palm is relatively square look at the lengths of your fingers when they are closed together. For comfort the 2nd finger is the longest, followed by the 3rd (ring) finger. Is the index finger shorter than the 3rd finger and is the pinkie up to or past the last joint of the pinkie? If so your hand should fall comfortably on the fingerboard with "pianist-shaped" hands resting on the pads, back from the tips. Look at your fingers side-on. Is there a flat-ish area between the tip and the middle of your fingerprint. This is what your fingers rest on if you simulate playing the piano and the area that you will bisect with the string. Thin pointy finger ends will not have this flatl spot.
A relatively short little finger means coming to the neck with a lower elbow but means that your elbow will tend to "ground" on the ribs of the bass before your LH thumb reaches the base of the neck (IV and V positions) and your arched pinkie will tend to point back up, not across the strings. It will also be perhaps weaker than if it is straighter but pointing across the strings.
So, experiment with the height of your elbow (preferably lower than the LH shoulder) and see what effect this has on the way your pinkie approaches the string. You may have to adjust the shape of your other fingers and experiment with changing from 1-2-4 to 1-2-3 around III position but there will be a way to maximize both comfort and efficiency.
Last edited by David Potts : 09-30-2013 at 10:23 PM.