Why you guys want to do the SSS conversion for the WP forks, it does not make any sense(Protune 1000$ with used parts and TBT 1700$ with new parts)?
You can get brand new Yamaha KYB SSS Factory fork from 17 Yamaha about 950$(or even less if you know friendly Yamaha-dealer), then you can buy from Technical Touch KYB WORKS KTM specific axle lugs and oil locks for around 400-500$(add 300$ bucks more, if you take new inner tubes as well, 450$ more if you take new innertubes with DLC coating). For 1400-1800$ you have brand new another fork that you can use and put the 4CS aside, then when you will sell the bike, just swap the crappy 4CS back and take the KYB for for new bike again, easy.
Yamaha SSS outer tubes will fit into latest KTM, you will have to use 0.5mm shim. If you do not want to use the shim just buy the Xtrig triple also from Technical Touch.
I have done SSS conversion few years back into one KTM, it worked good but it was no match to previous KYB SSS complete fork which I had in the same bike. I believe that flex characteristics is different KYB vs WP tubes.