If that parasite is designed slightly aerodynamic (with a total volume of lets say 5-10 tons) and you have a vessel with 100k+ GT, i dont think that the differe

If that parasite is designed slightly aerodynamic (with a total volume of lets say 5-10 tons) and you have a vessel with 100k+ GT, i dont think that the difference in fuel costs will be noticable - the difference due to tide/winds etc. will be much bigger.