Is there any concern to prune back lilly pilly and Murraya rather aggressive?

Question

I have two plants that have grown over the years without serious trimming/pruning. As you can see in the pictures, they have grown a lot taller than the fence.

I want to trim them back to about 0.5m taller than the fence. Is it too aggressive? are there any potential issues and cautions I should know of?

Murraya

And

Lilly Pilly