Mail 16.0 - new message opens large screen - how to stop new behavior?

Folks: Recently my Mail program is going large (not full screen) when writing or replying to an email in Mail 16.0, Sonoma 14.6.1. Intel iMac 27" The mail program stays the wanted size on my monitor, but I would like new or reply emails to stay the same size as reading an email. Can not figure... nothing in settings I could find. This has started in the last month. No particular updates that come to mind. Thanks! John