So does he curl his head under or invert it up? In what ways are he sensitive?
My boy can’t stand things that are loose in his mouth (loose rings of any kind, elevators, most jointed bits) so to jump we have a few options. A mullen pelham with a curb chain guard (he doesn’t like the open chain or how is jingles, so between the guard and the lip strap he is generally happy) or his favorite a mickmar combination bit. He has also gone in a slow twist but it did not work long term (he fixated on that rather than the job at hand).
For both bits I use two reins, figure 8 with the pelham, plain caveson with the mickmar (b/c of the port). In both cases, I use these bits to encourage lifting his shoulders without lifting his head as he is a known head flipper. A gag will lift the head (and can help lift the shoulders as well, depending on the horse)
ETA: what is the reason for changing from the dutch gag? (my sensitive boy hated it, didn’t last 5 minutes the last time I tried it, but it moved too much for his liking)