i am wanting a railed forend, but am stuck on 3 choices. KAC FF short, KAC ris, DD 7.0. how do the free float variety mount? if it is too much of a pain in the ass i might have to go with the RIS. i am seeking a solid forend, so i heard the free floated type are more of a solid platform. can someone elaborate as to why it would be more solid than the other variety? and would it depend on the gunsmith who installs it as to it's solidness? confused......................., anyone who can clarify will help alot! thanks!

Try quarterbore.com, he has a lot of details:
Quarterbore


Or Knight's website has install instructions:
Knight's PDF instructions

Knight's install instructions as a Word document

thanks for the reply. does the installation depend on the solidness of the unit?

Not sure what you mean by that, but I can tell you the KAC FF rails are very solid.  It does require the removal of the front sight base and flash suppressor in order to put on their barrel nut. Another FF RAS system that does not require removal of the FSB or Flash  hider would be the KAC RAS II.
I have use both and have installed both, the RAS II is far easier to install (only need a flat head screwdriver) and it seems to be just as strong. However the RAS II only comes in carbine length. Try this site:Quarterbore's RAS II page

I believe the Daniel Defense Rails are very similar to KAC's, however I have never used or installed any of those.

The only rail system that would be stronger would be LMT's MRP (the rails and receiver are milled as one piece)

thanks for the info!........again all these accessories and gear is hard to keep up with.