You have a good idea for the basal increments. Caleb has been using the Pod for three and a half years and was 4 when he started with a TDD of less than 2 units, so I understand the concern.
Rather than use 1/2 hour increments however, I would suggest alternating basals in hour increments. So if you want to achieve 0.225 over two hours, you would do that as 0.2 for one hours and 0.25 for the next.
The reason I suggest this, is because the insulin delivery is in 0.05 pulses on a conservative basis based upon 60 minute intervals. If you split it to 30 minute intervals, although mathematically it should work, I think you might lose a pulse here and there and deliver less insulin than you want.
For example, if you want to deliver 0.20 in an hour, the Pod will begin that hour and deliver insulin on the 15 minute, 30 minute, 45 minute and 60 minute intervals - the latest possible, not the earliest. If you do that for a half hour, you would get it at 15 and 30. If the next half hour is at 0.25, you will get a pulse in 12 minute intervals or at 42 minutes and 56 minutes and at the 60 minute mark it will start all over. You will end up with only 4 pulses in that hour when you wanted 5.
It’s actually a little more complicated than that because the 60 minutes don’t start counting at the start of the hour, but at the minute you activate a Pod. So unless you know that minute and can track this all out, I would suggest sticking with full 60 minute intervals to ensure you get all the pulses in the hour you want.
Did I explain that well, or just make matters worse?