norwegian,
for X-band WXR which has a slightly narrower beamwidth (for same antenna size) i use, -1° for target at 160nm, -2° for 80nm, -4° for 40nm and -8° for 20nm. i also noticed that on modern WXR, possibility due to the sensitivity timing control, if a range of 40nm or less is selected, the sensitivity level drops.
if you really want to pickup the most thin cloud layer you might need to leave your range at 80nm with occassional selection of 40nm range.
with most modern WXR also there doesnt seem to be any variable gain selection in WX mode. i find increasing the gain helps tremendously in pickuing out the 'best' track. so at times, i have it in MAP mode at max gain!
hope these helps.
SR