Neko's nadir was reliably between +3.5 and +13 when she was on Lantus, though most often between +7 and +9. I got to learn her BG patterns and could usually guess roughly where it would be. Data is your friend. And if you can't monitor, leave out lots of food for him so he can keep himself safe.
I would recommend picking one of the two dosing methods used here, either Tight Regulation or Start Low Go Slow. Following their guidelines for dose changes (and shooting lower numbers) will make things easier for you. Again, gather data when you are able to monitor, so you can learn what to expect.