It's not clear in the pictures but is that a chamfer with a recess grove? How easy is it to remove once the tin is empty.
Yes, the shape replicates spouts that come with the tins, but I had to make adjustments because the PLA isn't as flexible as the original plastic.
It'll be interesting to see it in action with the weight of 20lts pressing on the back face.
Yes, it will be interesting, the last one I tried was a little too easy to remove, so I tweaked the dimensions a little. It won't have the full weight of the oil bearing on it as the pressure will be relieved by the pour.
I did consider attaching a piece of cord to retrieve it should it drop off, but I guess I should really have faith.
If it doesn't stay in place, I have a cunning plan for a design a bit like a rawplug, where a spout will push in and splay out some pawls inside the tin, fixing the assembly in place.
I could find a use for one of those if ever I receive a tin of oil without stab holes in it 
I have two or three suppliers who don't stab the tins, but the thought was that I might give one to the people who do in an attempt to stop them doing it. To that end some sort of closing device could be a good addition.