Hi @Meise86, fyi there was a related discussion on this topic recently in https://opensprinkler.com/forums/topic/ok-to-hardwire-7-zones-7-x-24v-ac-valves-in-parallel-with-ospi/#post-78733 (last paragraph about “virtual zones”).
FWIW regarding your idea of total capacity = 1 and 0.1 and 0.2 capacities: I think that I would have difficulties in practice to estimate whether a zone would be 0.1 or 0.2. Of course, I planned my setup but it is also a lot of rule of thumb and best guesses and not too fine-grained. That is, more in the range of these steps: 0.1; 0.25; 0.5; 0.75; 1 or so. Just to give some feedback on the idea… But virtual zone do sound a bit more easier to grasp imho.