Crepe Myrtle advice

I'm in Adelaide and have 2 Sioux Crepe Myrtles that have been in the ground for almost 2 years. They were advanced plants when planted but they haven't really filled out as I'd hoped. I was after a "standard" look akin to this -
https://www.houzz.com.au/photo/6612668- ... -francisco

What I currently have is -




Trouble is there's been zero new growth from the main trunk in the past 2 years so I assume there isn't going to be any. It makes the trees very sparse and nothing like the look I'm after.

I'm considering doing something dramatic to force growth at the height I'd like by lopping/topping the main trunk just above the lowest branch. I'll lose the tall slender look but I'm hoping the tree takes off from that point.

I know this type of pruning is called Crepe Murder but in their current form they are pretty underwhelming specimens anyway.

Any thoughts or advice?

I grow these for a living in my nursery. You should do a yearly prune taking off 1/3. You will get more growth and more flowers from new growth. You can also give a harder prune occasionally

Thanks. I'm going to go the hard prune route tomorrow and lop off half the main trunk so that I can reset and hopefully get some growth outward so it looks more like a "standard" rather than a stick with some branches.