heres a little openscad scriot for playing around with teardrop shapes.
hit f5 to see the shape.
// CA's quick teardrop shape missile script
$fn=50; // facet number - if you don't know what it does, leave it alone
// adjust the numbers below to change shape of the teardrop
tl=40; //tail length
ttt=4; // tail tip minimum thickness
sdw=40; // adjust sphere depth
sdd=30; // adjust sphere length
sdl=40; // adjust sphere width
// don't change anything below this line - unless you know what you are doing
rotate([0,90,0])hull(){
translate([0,0,sdd/2])resize([sdl,sdw,sdd]) sphere(d=sdd);
translate([0,0,sdd/2]) cylinder(d1=sdw, d2=ttt, h=tl);
}