I should be able to pull the model at this point providing a force equal to the resistance, my tow rope pull should be, if I has this tow rope pull, I give a pull to the model, that should be equal to RT- is it not?- and applied at the same point that is, resultant point where the resistance works, as I have mentioned we do not whether resistance works, we only know that it can be somewhere in the middle of the ship, may be mid ship, and slightly less than half the draft, above the keel line- this is all we know.