If you hit the cap in the first semester and already have to take out at least a small loan, the GI Bill will then [as it appears with the situation you stated] pay out only BAH which means it's using up remaining benefit. If you're going to have to take out a loan for tuition for 2nd semester as it is, take out extra for living costs for that period just in case, so if you don't get voc rehab (or in time), you can use it for first semester again the following year and get the bulk of tuition taken care of again. If Voc Rehab comes into play, you'll be fine then on out. By doing it this way, lets say Voc Rehab (or rating) doesn't go through, then with having at least 1 day left, if you start a new semester (year 3 now), you should have tuition paid for for the whole semester (up to the cap). I could be misunderstanding how that works though, but I've spoken with people who have claimed that with only days-1 mont left, the GI Bill paid for the semester in its entirety.
So again: If the rating or Voc Rehab don't go thorough, or take forever, use your GI Bill only during fall semesters when tuition will have best coverage, and you're overall time of receiving BAH is the same (or a little more however, while tuition for a semester would be paid, I don't know that you would receive BAH beyond your actual last day of 33).