RE: Fin Quiver
Your plan sunds pretty good if you never sail anywhere with weeds or shallow sand bars.
The Serenity doesn't need quite so many fins.
I don't particularly like the 70 cm wide as I find it's simply way too much fin and makes the board difficult to sail as the 70 wide does not "transition" well from upwind pressure to downwind pressure.
As you roll the board from lee rail down (sailing upwind) to upwind rail down (to sail off the wind or jibe) the big 70 cm wide has a big bite on one side, kinda "floats" through neutral fin pressure, and then takes a huge bite on the other side.
58-62 cm fins are my favorites in the Serenity, but here in Hatteras I'm forced (by weeds and shallows) to use really small fins.
I sailed about 7 miles last nite in very lite winds with a 32 cm Tangent Dynamics Reaper. This fin was too small, but I still ran aground and had to turn the board around and sail with my weight on the nose to lift the fin in several really shallow spots.
The Serenity performs much better with a 36 cm Wolfgang Lessacher Duo (asymmetrical) weed fin, but the extra 4 cm would have prevented me from sailing where I wanted to go last nite. (Canadian Hole to Cape Hatteras School/Brigands Bay).
The stock fins are pretty good, and if the price is right, (compared to True Ames/Gorge Fin Co./Tangent Dynamics/used Tectonics Etc.) and they are available, the Drake/Deboichet fins are great.
Chuck Ames has some really nice larger fins, so check there as well.
You don't need custom fins, but if you can find some used customs for a reasonable price, that works as well.
Do I recall you live/sail in the Seattle area? If so, you are ging to love the Serenity.
In summary, I think you might be going after a few too many fins here.
F-158 needs 70cm; 60-64 cm; 52-56 cm and that' s about all you need.
Serenity needs 56-62 cm and maybe 48-52 cm and I think you will have virtually all conditions covered.
Hope this helps,