Yes - it can be achieved with custom CSS:
/* --------------- for better editor view ---------------------*/
#acym_wrapper #acymwysidtemplate center, #acym_wrapper #acymwysidtemplate table.container {
max-width: 800px !important;
}
/* --------- general width =)
after this is set and the the editor has updated to the new width, all new set images will get the new width
---------------------*/
#acymwysidtemplate center>table {
max-width: 800px !important;
}
i searched and tried all over, but this is working for me with a custom template, done with the builder
