boiler installation for two houses and solar

[chuppy]

Hello,
I am setting up two apartments one two bedrooms and one four in a house, the sloping roof is 30 ° north of the west.
There will be 3 bathrooms in total and between 5 and 8 people should occupy the premises.
I'm thinking of installing myself a solar system with a preheating boiler of + -200 liters next to the boiler in the attic.
The boiler instantly produces 28l / m dt30 °, which seems quite enough for two showers simultaneously.
For simplicity, I would take a non-pressurized panel system and the output of the solar boiler would be directly connected to the boiler to produce sanitary water.
From the simulations I made 12m2 of panels would be good.
does that sound correct to you?
I would add after having moved a little on the pipe passages, that I could place the boiler with the double flow in a separate room located between the 3rd and 4th floor (out of 5) alos the boiler would be fed by the solar roof balon by 10 m of pipes and the boiler would be more central in the building which is surely a thermal advantage. Only if the boiler is in this place how do you make the connection? Wouldn't that be a problem (air bleeding the boiler would be high point for some radiators and low point for others ...)?