Its something like:
h=10;ch=7;w=5; l=30; r=3;t=2; //ALL THESE ARE WRONG
difference()
{ union()
{ for(x=[l,-l]/2) translate([x,0]) cylinder(r=r+t,h=h); //The cylinders.
translate([-l/2,-w/2]) cube([l,w,ch]); //Center bar connecting.
}
for(x=[l,-l]/2) translate([x,0,-h]) cylinder(r=r,h=3*h); //Cut out holes.
}
`h` is the height at the cylinders, `w`,`ch`, is the width,height at the center section,
`l` is the distance between the centers of the holes, `r` is the radius of the holes `t` is the thicknesses around the holes.
Stuff this into
openscad save somewhere for the record, and change the values to what you need then hit F6 and export-stl.(I may be over pedantic now..)