Dividing up an island

If I purchase an island, am I able to divide it up into differently named plots? If so, are plot allocations preset or can the sizes be customised?

You can chop it in half, quarters, or a gazillion 16m2 plots of ya want. The only limit you have is that you have 65536 m2 to play with

But beware, it is not easy, especially if your new sim has mountains etc. There is no automatic way of parcelling an island sim. There used to be, via channel 4 of the RAW file, but that was stopped since around version 1.10 of the software.

There are also no commercially available tools to do this either, it must all be done by hand.

Rock Vacirca does this parcelling work for our Estate, and has developed some very useful tools to aid doing it, you might want to IM him if you get stuck.