No experience with Choco fins in the Atom 100 but can vouch for the Black Project Hammer's and Type R's 37.5, 35 and 32.5 are the three that cover 14-30knots for me, The Hammers in Powerbox are very new and you may have to email BP to source one, the type R's are readily available normally.
The BP's will let you push hard and resist spin out and go fast, in a straight line, so if that's what your chasing they are awesome.

JonesySail said..
No experience with Choco fins in the Atom 100 but can vouch for the Black Project Hammer's and Type R's 37.5, 35 and 32.5 are the three that cover 14-30knots for me, The Hammers in Powerbox are very new and you may have to email BP to source one, the type R's are readily available normally.
The BP's will let you push hard and resist spin out and go fast, in a straight line, so if that's what your chasing they are awesome.

+1

The Type R is highly spinout resistant, points really well, provides a heap of lift, feels good through gybes, and are fast.

What size sails are you using? The 37.5 could be a touch on the big side when using smaller sails. A 35 would probably cover you for most situations though.

http://www.blackprojectfins.com/windsurf-fins/windsurf-fins/race-fins/

From what I understood the Choco carbon fin has been developed by Winheller Prototypes, which I'm using in 38&32cm for my slalom setup. I would recommend getting the fins from Lars directly because he has already updated the fin and made some great progress in the last 2 years.
On the Atom, a 36cm should be a great alrounder.
~Shinobi

Have ordered a flying objects fusion 36 fin now cuss think be right for me and my shadow!