I have been into Slalom sailing for 30+ years, and have quite a quiver of older slalom sails. 
S2 5.0 Venom
MS 5.5 TR 2016
MS 6.3 TR-Xi
Loft 7.0 SkyBlade Foil 
MS 7.0 TR-Xi
Phantom IRIS RF 8,9,10
For the smaller slalom sails I've modified the clew with outboard eyelets above the long batten.
www.seabreeze.com.au/forums/Windsurfing/Foiling/Loftsails-Skyblade-2022?page=1
I have decided to go with Patrik's Race "SF" for Slalom & Foil. I think the modern design will be better than my old small slalom sails, while they should also be better in FIN mode if I switch.
e.g. Race SF 6.2 Luff 451, Boom 185 rigs on SDM 420 IMCS 21 idealy or 440.
c.f. Foil S2 "Slalom Speed" 6.0 Luff 451, Boom 183 rigs on SDM 440 IMCS 23 ideally or 420.
So they seem pretty comparable.
Benefits: 
In 5.0 and 6.0 conditions I can jump from foil to fin if it gets more windy. The Loft 7.0 has a deep foot so you need to add +5cm or more to the mast base to lift it off the deck or it sticks between the footstraps and you can't sheet out on a fin. Scary!
Less gear as I don't need dedicated fin and foil sails
'Should be' more stable on foil than my old S2 & MS sails
'Should be' better slalom sails than 6-8 year old designs
Obvious downsides is that a compromise sail is a compromise.
I had a fab time on SF 6.2 last yr in Albany. Patrik will have twin cam sails available too. I think they are fin first but will also work with foiling. Not sure if I should post a pix of when I saw the on the water. Looked solid construction and just like they should for the Patrik loft.
Here is a comparison... from file photos...
Dedicated Foil Speed Slalom S2
Slalom or Foil SF
Overlapping... showing the obviously lower foot on the dedicated foil sail and the looser, longer leach on the slalom fin/foil cross over sail.
When considering the differences (and similarities) between fin & foil slalom sails, outline is indeed important (clew position, aspect ratio) but so are profile, tension distribution, and the position of the center of effort. On the other hand, other features may need to be more similar than one might think: like on fin, the difference between actual wind speed and board speed decreases as the wind increases, which would suggest more similarities than differences in the need to loosen up the leech in smaller size sails.
After a few sails with the Patrick Race SF on both fin and foil I can provide a few details.
TLDR: These sails feel 100% fin slalom/speed compatible and 90-95% foil sails.
My comparison is to larger 2022 7.0 Loft SkyBlade and 2020 8.0 Phantom IRIS RF pure foil sails and 2021 Loft RacingBlade 7.7 and various Maui Sails slalom TR? 2014-2018 models and sizes
On a slalom board the sail feels perfectly at home with great power and stability. Throw them into a full speed gybe and they rotate easily getting you back up to speed! I'm pretty sure you could push these sails past 40 knots on a speed run.
For comparison my experience of the SkyBlade 7.0 on a slalom board was that it had a distinct lack of bottom end power and didn't really pump on fin up to speed at all. The short boom not helping!
On a foil board some of the softness that makes the SF's so comfortable and forgiving on fin is noticeable as a small movement in the sail profile as the leach breathes. Below 25 knots and/or just cruising this isn't really noticeable at all. but if you are pushing for 30+ knots on 400cm2 or smaller foils like those from F4! Then the minor movements are noticeable as you push. It is very manageable but just shows the weakness of a compromised cross over sail at the extreme edges of the design envelope.
The cams are a work of art! On the beach you can NOT push them around by using your fingers against the cam, they are solid! But on the water or with a bit of batten assistance the cams SLAM around with certainty!
I rigged the 5.0 on a Severne SDM 400 while the 6.2 was mounted on a Maui Sails 430. Both claim to be ~CC.
Overall if you want a sail that you can ride on foil until it gets windy enough to swap to fin then these sails are perfect. 
Thanks to Gergio for the slalom board loan.
