We have planned approximately 45cm seat depth and 90cm width. The partition to the WC will be rebuilt, so the attached plan does not yet correspond to the dimensions mentioned above.
The shower is 1.1m wide and a total of 1.8m deep, so splash water is not a problem, and if necessary, a walker or wheelchair can be moved a bit further away so that it does not get completely wet. We quickly decided on a mineral cast shower tray measuring 1.6x1.1m. It has the advantage of eliminating the sealing issues caused by tile joints that become leaky over time; the material is dyed throughout (can be repaired with colored resin in case of damage), and the surface of the chosen tray is quite rough (non-slip).