I doubt if anyone here will have walked the GR20 in the past week or so. Starting on 11th May is taking a big risk. I once started at the end of May and found a lot of snow and ice on the route. I was fine, as I had ice axe and crampons, but at one point I was kicking steps up an unbroken snow slope for 2000ft. I met three English guys who were on their third attempt, and each of their attempts involved starting at the end of May. Their previous two attempts had to be abandoned because of snow and ice so early in the season, but the were lucky on their third attempt. I think you might find you need all the luck you can get, starting so early in May. Remember that the refuges won't be staffed (though the doors will be open), and you'll have to carry all your food for several days at a stretch.