I don't know about palms - the biggest problem with those seems to be the fiberous nature of the thing. I haven't cut many, but as I recall they just jam the saw up. I think the best weapon against that would be a really sharp chain, probably .050, and cutting slowly.
As for the bar we just use the ES bars as they are good solid bars. We used to use hard nose bars because the conventional wisdom was that cutting roofing material would gum up a sprocket, but long ago I decided to test that, found it to be BS, and we have been using sprocket tip bars ever since - 15 years or so - with no issues. With a hard nose bar it got way too hot and the chain would stretch beyond imaginable limits causing a variety of problems.
I just order chain from a Stihl dealer like any other parts - seems to work out fine. Dealer cost is $921/25' of RDR. About half that for RD.
