Alpinisto wrote:I'm worried about the slipperiness of the Dyneema (not to mention the wide surface area of the sling) not biting onto the rope.
Give the FB-sling knot a (safe) try and see for yourself. The reason why it works is explained in the link that Herr Bachmann posted. The fact that the sling runs freely through the loop formed by the overhand helps in translating the load into friction force and also makes the loosening of the hitch easier once the sling is unloaded. The flat sling also wraps around the thin rope more easily than cord.
As a disclaimer addressed to everybody in general and no one in particular, master each technique and know its limitations before committing your safety to it. Don't use a Dyneema sling in any application in which significant heat may be produced through friction or otherwise transfered to it.
Examples: Ascending stuck rappel ropes: yes. Rappel "third hand": no. For glacier travel, I'd still pre-rig Prusiks, because I have not tried the FB-sling knot on frozen ropes.