Hi Don,
about practicing cutting the headstock, that's an excellent idea and that cut looks great.
However I wouldn't just practise cutting the shape of the headstock; get familiar with your tools and with different types of timber. Practise on timber with different thickness as it will respond differently (I might be wrong but the timber in the photo you have attached seems much thicker than a headstock).
Practise also cutting precise 90deg angles, or cut a long straight strip 1cm wide and 20cm long.. cut a circle, cut free hand shapes, cut 90deg angles then try to round the edges, and so on... this will get you familiar with your tools, will make you comfortable with cutting and correcting different shapes, and will give you a sense of how different timber responds and vibrate.
About vibrations, when you eventually will cut your headstock, make sure to clamp the neck as close to the headstock as possible, to avoid excessive and unneeded vibrations that could potentially crack the timber.
I usually use two clamps, I make a sort of sandwich with the neck in the middle, some cardboard and some scrap wood I have around (plywood or anything), to avoid leaving the clamps marks on the neck.
If I am cutting a bass headstock (for example a classic Fender precision headstock for example) I put two clamps slightly apart where the low 'E' and 'A' tuner will be.
I am not sure if Tasmanian oak is similar to maple, however I would proceed in a similar way. Get familiar with sanding and do test painting on as many scraps of wood you can find (without breaking the bank!).
When you will cut the headstock, there will be the parts that you have cut out that you can use for painting and finishing tests.
For the body, I usually do my tests inside the electronics cavities. These are small surfaces compared to the back of a guitar body for example, some tests might not be 100% accurate but they will still give you a very good indication on how that timber will respond and look.