Most authorities recommedn wearing a "wide-brimmed" hat for sun protection. How wide is wide? I was wearing a 3 inch brimmed straw hat the other day and it seemed to provide full facial protection till pretty late in the day like 4:00 p.m. WOuld the additional protection afforded by say a 4 inch brim be worth the extra brim? It seems like most hats are about 3 inch brims. is this what the hat world has generally decided on as a reasonable compromise for sun protection suring the main sun hours? why not 4? I'm trying to decide betwee a 3 and 4 inch tilley.