Another design assistance request.

[Roxy]

If you load this into Open_Scad, it approximates the shape you are looking for... In order to actually use it, you would need to add more points to better define the shape. The red circles are there so you can see how the cut_out() is formed and to make it easier to play with. Adding the # symbols to the side_profile() module might be helpful to get its shape closer to what you want.

After the side profile is defined, a large block of that shape is made at [10,0,0].

side_profile();

difference() {
translate([10,0,0]) hull() { 
    side_profile();
    translate([0,0,5]) side_profile();
}
translate([10,0,0]) hull() { 
    translate([0,0,-.1]) cut_out();
    translate([0,0,5.1]) cut_out();
}

}



module side_profile() {
difference() {
    main_body();
    cut_out();
}
}

module main_body() {
hull() {
    translate([0,1,0]) cylinder(r=1, h=.1, $fn=30);
    translate([1,0,0]) cylinder(r=.25, h=.1, $fn=30);
    translate([2,.5,0]) cylinder(r=.5, h=.1, $fn=30);
    translate([3,1.5,0]) cylinder(r=.5, h=.1, $fn=30);
    translate([3.25,2.5,0]) cylinder(r=.5, h=.1, $fn=30);

    translate([3.5,3.5,0]) cylinder(r=.25, h=.1, $fn=30);
    translate([3.0,4.25,0]) cylinder(r=.5, h=.1, $fn=30);
    translate([1.75,4.7,0]) cylinder(r=.5, h=.1, $fn=30);
    translate([1.5,4.5,0]) cylinder(r=.25, h=.1, $fn=30);
}
}

module cut_out() {
hull() {
#    translate([-1,2.75,-0.01]) cylinder(r=.5, h=.2, $fn=30);
#    translate([1.,2.15,-0.01]) cylinder(r=.35, h=.2, $fn=30);
#    translate([1,3,-0.01]) cylinder(r=.25, h=.2, $fn=30);
#    translate([.75,4.25,-0.01]) cylinder(r=.25, h=.2, $fn=30);
}
}

But probably, it might make sense to make the shape nice and smooth by starting with a couple of spheres and scaling different dimensions and then putting a hull() around that? Do the work with 3D objects instead of doing a 2D object and making it 3D ????