Best approach for using 2 displays to show a whole single frame?

[defavltt]

Working on a project where 2 displays(128x64 lcd's) should be updated together by chip selecting one, writing the data, then chip selecting and updating the second one in the same way.

The main drawing wide buffer should be 256x64, and be modified with the u8g2 drawing routines.
Initially I tried doing this by first setting the buffer pointer to the wide buffer, drawing some frames and then calling setBufferPtr(wide_buffer), sendBuffer() and after a period of time calling setBufferPtr(wide_buffer+((128*64)/8)), sendBuffer() to display the second half. This is done on a single screen for a quick test, just need to see both halves alternating on the display. Im sure this is not properly done, thats why im not seeing anything from the second half. Since the u8g2 drawing routines are limited to the current screen resolution.

So is there a way to change the current resolution so the drawing routines can draw on the whole custom buffer? And even if that works, will just offsetting the address by the size of a single display buffer for setBufferPtr(), properly align with the tiles?
Also how can I change the current CS pin on the fly, without calling begin() again or using a second constructor?

I know my approach is a bit hacky, so I will be happy if someone has a cleaner way to achieve this.

[olikraus]

There had been a discussion on the same problem here: #1351 (comment)