Oday 630 -
This all depends if your present batten pockets are 'adjustable' .... and how SERIOUS you are about 'performance'.
Adjustable batten pockets typically have adjustable VELCRO 'tabs' at the leech end of the batten pocket. This allows one to set varying amounts of compression along the batten length - the more compression - the more 'fullness' of the sails draft; the least amount of batten compression - the flatter the sails draft.
A sailor looking for 'high performance' usually will set up batten compression to the 'days' sea state and wind conditions ... usually MORE batten compression (fuller draft - 'power') for higher waves/chop, Less batten compression for 'flat water' (a flattish less drafted - 'speed shape') .... inspite of how much wind is or isnt blowing, and ignoring the amount of heel, etc.
With adjustable batten pockets one can also adjust for the 'amount of shoulder' (power/speed characteristics developed at the 'top' of a sail) .... more 'shoulder' for when sailing with large crews that can 'hike out', and less 'shoulder' when less aggressive sailing is desired, etc.
Setting up for differing 'twist' due to differing vertical wind gradients (depends on air density, air temperature, relative humidity, etc.) can be easily accomplished by varying the amount of batten compression (from the topmost batten down to the lowest batten), especially with 'long' or 'full' battens.
The proper amount of twist for 12-15kts of wind strength (~11° of twist) is usually already inbuilt to a mainsail by the sailmaker (and depends on the angle that the boom makes with the mast - typically set for 87-89°) but twist can be tweaked to meet slightly varying conditions. This may be 'splitting hairs' but the fleet leaders in serious racing venues usually do this ... hence the evolution of 'air battens' so one can alter the flex characteristics of the battens while 'on the fly' and in concert with adjustable mast bending - especially when using 'full' battens or "2 long + 2 full" set ups.
If the batten pockets arent adjustable, then for 'high performance' one should have several 'sets' of battens of varying stiffness, slightly longer or shorter length (compression characteristics when in the pocket), and varying flex characteristics, to match the present 'days' sailing conditions.
Also, tapered battens dont 'wear out' the forward section of the batten pocket as fast as a non-tapered batten which 'flexes' or creates a 'hard spot' in the sail material at the front end of the batten pocket on 'short' and 'long' battens .... so, in my mind, even 'short' battens should be well tapered to prevent undue wear and premature failure of the front section of the batten pocket and underlying sail material. Different 'tapers' on full battens can also affect exactly where the *point of maximum draft* occurs - important for precise 'helm balance'.