offset pipe reducer (customizable)

I thought I would need to make an eccentric pipe reducer recently for a new cooker hood ductwork. OpenSCAD's cylinder command doesn't allow the axis to be skewed so I didn't model it. Fortunately we were able to fit the ducting without it.

This model allows the user to specify two pipe inner diameters and wall thicknesses. The upper pipe can be offset by a percentage of the radius (0% is concentric, 100% is fully eccentric) and the centre can be rotated if required (though both axes run ve