Rather than focusing on light wind sails, etc., I would suggest that precise trim, sail SHAPING, and boat underwater condition would be much more 'profitable' than any new sails by themselves.
Such suggestions will result in better light wind performance than anything else ... and possibly with what you already have
in your current inventory.
I dont know your 'expertise' at all; but, the usual course is to start with such as: Sail Trim Chart and Sail Trim Guide
...... to learn how to PRECISELY trim so that any sail that is flown is operating at its maximum output. And, then progress up through advanced trimming and sail shaping
until your boat is 'flying' in light winds. Much of this advanced info is available on the web and isnt usually found in 'how to sail books', etc. :
---> magazine articles --->
Checking Trim on the Wind, November 1973
Achieving Proper Balance, December 1973
Sailing to Windward, January 1974
Are You at Optimum Trim?, March 1974
This 'process' will include good bottom prep, including SMOOTH
bottom paint, and a relatively CLEAN hull, etc.
And THEN once you gain 'mastery', you can consider sails that are designed and cut for your
'exact' wind and wave conditions .... the sails are made exactly
to YOUR helmsmanship ability, and exact sailing venue
needs and requirements.
This would include the use of 'racing cut' sails with 'fine' or flattish luff shapes, etc. etc. instead of the 'one sized fits all' *cruisers cuts* (stock, plain vanilla sails) that are only applicable at 12-15kts of wind strengths .... and are built as 'forgiving' for the 'inattentive' helmsman in mind --- always a 'sad' compromise, especially for light wind sailing.
All this 'starts' by the usage of a FULL set of tell tales, including "gentry tufts" ... and there isnt any other way to do this !!!!!!
Gentry Tuft System
A Truer Tale of Telltales
..... and this is 'just the beginning' of a long process to build 'bombproof expertise' of how the wind is 'flowing over the sail surfaces' and what 'shaping
' of the sails is required to get this 'maximum'.
For those just "entering" this process of sail trim and sail shaping 'mastery', there is a fairly decent forum discussion: Sail Trim with Don Guillette - SailboatOwners.com
Its an open forum, so you have to decide for yourself whats applicable to you, or not.
That 170 you have ... probably the WORST thing for the super light winds !!!!!! .... not enough energy in 'very light' winds to keep the air flow streams 'attached', and why BIG %LP jibs and genoas have virtually disappeared from usage.