A few thoughts:
[ol 1]
[li]Will the inside also be exposed? If not, perhaps you can come up with a detail with the hurricane tie on the inside and not visible from the exterior. If you do this, be careful that the connector can transfer the load into the exterior sheathing without relying on cross grain bending of the wall top plate.[/li]
[li]I could be wrong but thought Simpson might have a nice looking hurricane tie, painted black. If not, maybe they can just paint an H3 black.[/li]
[li]Perhaps you can screw the rafter to the top plate from the bottom.[/li]
[li]I wouldn't try to screw it from the top down[/li]
[/ol]