Marty:
Yes, you do need a longer screw after the suction cup mod, something about 1/8"-3/16" should do. The idea is to space the mirror's ball (on the back of the mirror) farther away from the socket in the mount so that it gains a little more sideways aiming travel. If you use the original (now too short) screw, it'll pull the ball too close to the socket and limit the movement. I know it's not much of a difference, but it's ALL the difference.
As a last resort,you could take a Dremel with a cut-off wheel to the car-centerline side of the Aero mirror mount, to remove a little material along the lip in a small crescent shape, such that you get a bit more movement over there, but the suction cup spacer should have given you that (OK, so mirrors are placed in different parts of the car, some needing more movement. Use your own judgment).
I didn't say I didn't like bullet mirrors....I just think that they just look better on some cars (typically, British) than others (Italian and German).
On the other hand, if you HAVE to have one or two on there, they seem to make more sense on the door than out front on the fenders. Whoever had my wife's old Healey before us didn't take any chances: Had two mounted forward on the fenders, and two more on the forward part of the doors (along with the usual center-dash rear view mirror). Do you think that all those make the car "Backward looking"????