Hi akaktto,
If you know you have been able to model the configuration, what makes you think the capacitances you have calculated are not correct. I would like to highlight that the value of the capacitance will not only depend on the absolute dimensions of the plates but also their relative dimensions to each other and the dielecric (aspect ratio). Beyond a certain limit, this causes fringing effects which may or may not substantially affect your capacitance. For more info, refer to this article:
https://nvlpubs.nist.gov/nistpubs/jres/22/jresv22n6p747_A1b.pdf
You are navigating away from the AIS Discovery experience