1750 is probably his sterling silver temp... not oven temp
Using an Electric melter. The melter can be up to 50 oF off so thats not really the problem.
Flask temp for a thick piece doing Vacuum casting is around 800- 900 oF
If it's a thick piece, you want to add some vent rods so that you can vacuum the residue out of the cavity before pouring metal into the flask .
With Plasticast, use 36/100 investment ratio, let sit at room temp (around 70 oF) for 2 hours... go through your normal burnout that has worked for you in the past except, go to 1450 oF and hold there for 3 to 4 hours before dropping to casting temp. hold at casting temp for 1 hour to stabilize the temperature within the flask. This is where you would vacuum the interior of the flask, then put it back in the oven for 15 minutes.
Now cast and we can all ask the casting gods to be benevolent