FFmpeg resizing webcam overlay on desktop

Hi there I’m trying to record my screen putting the webcam as bottom right overlay on windows, which works ..
But the webcam overlays video size is more than half the desktop size, and I want to resize it at 320×160

ffmpeg -y -f gdigrab -rtbufsize 700M -offset_x 0 -video_size 1920x1080 -draw_mouse 1 -r 24 -i desktop -f vfwcap -rtbufsize 300M -i 0 -r 24 -video_size 320x160 -filter_complex 'overlay=W-w:H-h' screen_webcam_bottomright.mp4

Any Ideas ? Thanks a lot for any clue, enlightment, notice ):