At 1.3 ozs. it is not that heavy.
Many alcohol stoves hold an ounce. It really depends on how you like to cook and have your hot beverage. If you freezerbag cook and don't drink coffee, tea, or hot chocolate, then 18 ml (.6 oz.)is plenty. Or you could just refill it once it goes out for your beverage.
I will try to dig my stove out and post a picture. I don't remember why I don't use it. I've made many types as it sounds like you have.
I think chimney type stoves are great. I don't like stoves that have to prime or heat up as well as those that don't need to. Plus, this stove is easy to light, fuel efficient, and hot.
Have you played around with the pot stand height? In the picture it looks like the pot might be too close. If you have more hardware cloth, I would make another pot support one square higher and see if that changes the boil time +/-.