edit layers

click on the lamp of the green layer to hide it

.InterpCrv the yellow

set point with osnap near in places 1,2,3

Mirror

set 1 point in osnap end

Ellipse:Diameter

in the place of the yellow ellipse

Edit Control Point Weight

change only in place 2,3,4 the weight to 4

Align Objects- the parts in the top view and choose HorzCenter

Sweep Along 2 Rails

Don't choose the point in the end of lines 1 and 2 otherwise the Twist command will not work

check the Maintain height in the Sweep 2 rails Option Menu.

Sweep Along 2 Rails and choose the point and the yellow ellipse

in the same options as above

Don't join the two parts otherwise the Twist command will not work

only select them

Twist

Join the 2 parts now !

Change Object Layer select all the lines and points that we don't need and put them in hidden layer(green)

Ellipsoid From Foci

Cutting Plane

Cap Planar Holes

make it on the two parts

Polar Array

Boolean Difference then

Move the prop out side like in the front view

Do the same to the other props

make the holes deep so you can Fillet Edge with 0.8

Surface From Planer Curves

then Delete the circles

Blend Surface

Join the 3 parts !

That's it !

You can make any kind of profile , and you can twist it as you like.

Good Luck!!