Should I "stiffen" outer wall?

I wasn't sure if I should start a new thread or continue on with the "Densglass Alternative; Apology.." thread. Anyway, on my metal bldg I ended up putting some of that reflective insulation directly against the metal (on the inside!). This stuff is sort of like bubble wrap with aluminum foil on both sides. Then I attached OSB to the horizontal runners that run between the vertical 6x6 posts (post spaced 10 ft. apart). Caulked all the seams. Then put insulation on the OSB. I will build a new wall (with airspace) inside of this. This sort of seems like it would end up being a 3 leaf system (metal-small air space, OSB-new wall), but the advice I received earlier was that the metal wall is so thin it could be deemed insignificant and just about be ignored. Hence the OSB. The small air space between the metal and OSB is just the thickness of a 1x6. Metal on one side, OSB on other. Just trying to add mass to outer wall. O.K., my question is this: Being that the 6x6 post are spaced 10 ft. apart, the wall has a little "flex" to it. I mean, you have to really push on it to feel it move, but is does move a little. The insulation is already on the OSB, but I could probably pretty easily space some vertical 2x4's in between the post to stiffen the wall up a little more. Just wanted to make sure it wasn't one of those things that someone would come back and say later "you should have left that outer wall ""loose"". The new interior wall will be 16" centers. I hope I made myself somewhat clear. I would put a link to my previous post but I'm not sure how to do it. I have some pictures and drawings on that other thread. If I should have continued on with that same thread let me know. I could copy this there and delete this thread. Thanks for any advice. J.P.