I wouldn't go lower than 0.3 TBH, without taking/sag losses into account, you'll be pulling 28a at 0.3. and it'll be a fierce vape at circa 230w. Personally I'd build nearer to 0.4, which is still a powerful vape, and see how you get on? Easy to pull a couple of wraps off the coils if you do want to go lower.
The Samsung 20s are cracking cells for mechs, not had the pleasure on a series device with them yet, but I use them in my single cell tube at 0.1 and they perform excellently. Be aware though that they have a tendancy to fall off a cliff if you run them too low - I ran one as low as I dared purely as a test, good performance than virtually nothing, checked the cell and it was quite warm, not roasting or untouchable, but warmer than I'd like - so don't run them too low, that was a test on my part fuelled by drunkeness to find out how a 30a build with a 30a cell performed, and the usable battery life at that level of performance. I only tested it once, but the drop was fairly immediate so keep an eye out for it - I generally change my batteries out long before they need it on mechs as I've plenty of cells, but I like to know their lower limitations and how they respond so I can keep away from getting to that point.