If you look at your relaxed hands and simply take that form (supported) to the bass... those I call "Forms-at-Rest." Same holds true in the way one sits or stands. If you can make those stances look as if you would take that form "naturally" then you're getting to what I believe are the most efficient forms for yourself. A few other things I do to keep irritation at bay: I pivot (LH) and rarely, if ever, stretch the fingers beyond the hand's width of palm. When one stretches or flexes fingers open, beyond the width of the palm, one stretches the muscles across the hand which puts stress on the tendons that are operated (as you know) by muscles in the arm, which are attached to the elbow. So those tendons can be irritated by the pressure that the hand muscles put on their movement. Likewise, the muscles in the shoulders press down on the shoulder when we raise our arm beyond shoulder height. After years of this the bursa (sak of fluid) which protects the shoulder bones from being crushed or worn-down by the muscles can become inflammed: bursitis! So I do not raise my arms over shoulder height. This means I must, for a low f on the e string, lower my elbow and place the hand at a moderately severe angle to the strings. This makes vibrato less wide. For a long time this is the position, but for a short duration, say for a wide vibrato on a relatively short passage, I raise the arm up. For the bow, I generally maintain a look where the hand is "hanging" from the arm (French) and the arm is always OVER the stick. I do not prescibe one position tho' for all strokes. Legato may be torqued forward whereas spiccato less so, towards the frog.
Awareness of the feeling of stress and/or irritation is the critical thinking part that helps establish more efficient, personal, forms.
Ciao! and Stay Cool!
PN
Tendonitis 
I am very curious to hear about this 'at-rest shapes' business. Thanks again.
more on form 
