i have optimized vertex cache hit of triangle strips and i got a boost of 10 Fps ( + 25 % ). I discovered pixel artefacts in the middle of grids ( not T-Junctions ) and post about it on gamedev for help, http://www.gamedev.net/community/forums/topic.asp?topic_id=437850. Normals update don't work yet, just a matter of time.
Edit : No more T-Junctions and pixel artefacts, those were Mipfilter artefacts. Normals are now correct but i will have to use the last row and column to get correct normals for clipmap n=255. Thinking about a way to manage this.