is the metatarsalgia focused on the ball of your foot? have you tried cutting out some of the sole to relieve the pressure on that area? I've never had that type of pain but thinking simplistically, seems like it might help. same idea as a blister cover on ball of foot . . .
cutting away might cause more irritation at the edges? but correct, either add padding, or adjacent support to take pressure off. Also, stay away from tight shoes that add pressure.