Yes, it is. 5 is clearly too much. 4.5 is too much. Today is a puzzle. Was there a lower number in there and then a bounce before +10 or was it flat and pretty high all day. Robin's puzzle analogy fits beautifully. It's like the pre shot tests are the edges. You can get them all, but it doesn't give you much of a clue what the picture is... You need the middle pieces, in the middle of the cycle.
If he were mine, I'd stick with the 3.5 another cycle and wake up and get a number in the +5/7. If he is not coming down much, then you could try 4 tomorrow am (assuming he is still in the pinks or higher). If you see a 50% drop tonight, then stick with it another cycle. Or you could do 3.5 for tonight and tomorrow and, he is still running high, start your curve on 4. What's your gut say?
It's difficult. You don't want him sitting in high numbers, but you also don't want to miss a good dose and increase and start the roller coaster again.
BTW, are you getting ketones tests? You should get once or twice a week, especially while he is in high numbers.