Will I have DV problems with a little more lift?

Hey guys!
I have an RE 5.5 longarm lift. I was wonderin if it would cause any problems to lift it another inch or two with either a small blocks or extended shackels and ACOS spacers? Will I have to get a longer driveshaft, or will the one I have do fine? And will I have more vibes? what could I do to avoid the vibes? thanx in advance!

I started with 5.5 and 33's, and everything was perfect. Went up and inch and a half with 35's, and everything got worse. The vibes came, steering sucked, unless you upgrade. Now I went back down to 5.5 and everything is okay. Still running 35's though. 5.5 is all you need for 35's.

do you already have a sye and ds? if so, you could squeeze 2" out of it, but you should shim your axle accordingly.

I have about 6.5" lift or so. with out an sye, t-case drop, or driveshaft mods. No vibs either.