I just use a converted kitchen ladle for ingot casting.
Well, it will cast 3lb dive weights, at any rate - was too lazy to fab an ingot mould last time! Going to make one out of a bit of 100mm steel channel, later on today.
No, I've given it some thought, and the mid hole version will hold more lead without spilling.I would give that one a run before making the second generation model, a bit of use will highlight any modifications that might be needed.
That's also a job for later on today, once it warms up a bit out in the shed - local weather station shows 3.9 °C just now...