Ahhh the million dollar question.
George was on lantus and he nadired as early as +2 and as late as +13

He most usually nadired at around +5/+6, but nadired anything in between, it's not really until they are well regulated that you find them nadiring consistently at a particular time.
Seriously their is no way of telling for a particular cat.
How are you fixed for getting data during the day?
If you are available all through the day time cycle I would start by routinely checking at +3/+4 and at +6/+7
If the numbers warrant it you can step up the testing, so if you tested at +3 and you saw a large drop you might follow up with a test at +4 or +5, same for the +6 if you found he was dropping with respect to +3 then follow up with a later test to see if he is continuing to drop or if in fact he is on the upward swing.
I would recommend that you always get at least a before bed test in the pm cycle, and follow that up if you feel you need to, ie if you saw a large drop.
Gathering a little more data consistently will allow you to make confident dosing decisions.
Based on the data you have at the moment, I would not take the dose up yet. Unlike prozinc with Lantus you need to determine how low this dose is getting him, and so far we do not have a clue, anything could be happening. We do know that he got a green on the 1u not so long ago though....
How you go about adjusting the dose will depend on which of the dosing strategies you want to follow or is a good fit for you. Have you read the sticky on the dosing methods? Which one are you hoping to follow?