I had changed the mechanical Tost drum brake on my Ventus to the hydraulic drum brake from Tost.
Don't. It's a closed hydraulic system and a massive pain to bleed (and the hydraulic hose connections don't aspire any trust in terms of leakage). Even if there is no air in the system, you still have a drum brake.
Changed to the new Tost hydraulic disc brake 3 years later. 1800 Euros plus work, but it's a very good system.

Bert
Ventus cM "TW"