Your settings sounds similar to what I used for my raised bed last summer when I was trying Flex daily to irrigate it. If you’re expecting deeper watering you might look at the root depth setting. Increasing it will increase the runtime, but also spread apart the intervals. To increase the amount of water you deliver without changing the interval, drop your custom nozzle precipitation rate.
I’m surprised that you’re doing OK with twice a week. I was at every day here in the desert, but our temps were higher and maybe drier air. I eventually moved to a fixed schedule for my pots and veggie garden, based on a recommendation by a resident expert here, @sunny. In my case I needed to water more than once a day and Flex daily is limited to watering only once daily. If you’re interested in reading more, check out Dante’s Garden.
If you decide to play around with Flex some more, take a look at this article. The ‘Zone Attribute’ table about midway down is particularly helpful.