I'd stay away from using LCs tubeless- the main reasons tubeless tyres either fail/burp is due to sidewalls not being flexible enough to cope with bumps, thus causing the bead to pop off- and one of the reasons people use LCs (as far as I know) is that they are really tough casing tyres, (and hence have a stiff casing)
Another issue you'd likely encounter is the bead itself making it hard to seal- its pretty much unheard of (as far as I know) to use steel beaded tyres tubeless, since the bead itself is less conforming to the rim, thus harder to seal. Its also more likely to be deformed/bent slightly, and this hard to seal, and also easier to pop off.
CX Magazine has a good listing of CX tyres that work well tubeless- though none of this was written with the epic 3P course in mind!
http://www.cxmagazine.com/going-tubeles ... mendationsYou'd probably get a very slightly better ride with tubes in LCs on Crests since the inner width of the rim is much wider than most road/cross rims anyway, and may (emphasis on may) be able to run slightly lower pressures.
That being said, there's little reason not to try the setup for a few weeks on some rough ground and see how it gets on. I'd be interested to hear the results.
Disclaimer- its my first time riding the 3P, so my knowledge about what would be best for the 3P specifically is obviously dependent on what I've been told!