Is it possible to force partitions to be primary or extended in Anaconda?

Issue

At the moment anaconda is choosing which OS slice to place either in primary parition or on extended partition.

Which is a problem because it's put / on extended partition along out /local/0. We want the option to extend /local/0 so we want to be able to force disk layout so that -

partition 1 is /boot
partition 2 is /
partition 3 is /var
partition 4 is the extended partitionpartition 5 is swap
partition 6 is/local/0

Can we do this?