Well, but, from what you stated, you don't disagree with the current rating, so it seems you may not have a real fight with the Army.
A few points. First, the mandatory minimum for PTSD is 50% for six months. You are, apparently, in a different situation where you were rated at 70%. Seems to me the "normal" 18 months review should then be applied, not the six month review under 38 C.F.R. 4.129. Now, here is another important point- one that has not been well implemented as of yet. The "new" (Dec. 2011) DTM 11-015, states that the ratings for IDES cases and TDRL will be done by the VA. I think the military is currently ignoring this and supplying their own ratings (I have fought this once so far, in a Navy case, and though they would never concede the point, they gave me what I asked for, continuation on TDRL for another 18 months...if push came to shove, and they refused to refer the case back to the VA for rating, I think it is a very winnable case). The point is that the VA is far more likely to continue or raise a rating than the military.
A lot of complicated issues. I tend to think that you won't do better or much better in fighting now- but you might. Again, I would not hazard a guess unless I knew everything about your case.
Best of luck on getting the proper outcome. I hope all goes your way!