I use 50lb on penn 850s and still catch fish

my heavy beach gear has spools of 8kg mono, 15kg mono 20lb braid and 30lb braid. the 20lb braid is the best for surf casting and unless your going for sharks it will stop any fish, get heaps on a surf reels spool as well. my tailor flicky is just the same as all my river flickys for flattys and bream.

I tend to go a fair bit heavier generally.

For light spinning and just tailor I usually use 15-20lb braid with a 20lb low stretch or flouro leader

Bottom fishing - I run 40/50lb braid through to a 50/60lb leader on the heavier gear when I need to lump out bigger baits or as Crezz says when Sharks are either a target or a possible by-catch.

Since the braid is already of a significantly slimmer diameter than comparable mono, the elasticity of the leader and good compression of the rod do all the work for casting, and I have the confidence I can put a lot of pressure on fish to keep them out of snags when neeeded (not so much a Metro issue, but there is plenty of reef up past two rocks).

I find leader length is important, for distance casting 15m approx works for me for surf fishing, but a general guide would be enough to have several coils on the spool with the rig hanging a few m's off the rod tip.

The above is all for spin gear, Im yet to start trying my Trinidad OH.

http://www.youtube.com/watch?v=pi4BE-vNqPE

I would much prefer to use a lighter braid for surf casting, say 10 or 15 lb, but find I have to use a heavier braid, 30 or even 40 lb,  to cope with the ocassional 25kg clumps of seaweed  I catch.

 I use the FG knot almost exclusively now and it has never failed me, however the knot length is important and does affect 'castability'.

The video below really helped me:

http://www.youtube.com/watch?v=52uWL43hUbw

its worth looking at a couple of other videos on the FG that go into more detail about knot length etc, but a reasonable estimate I find works - 15mm - 20mm (20 for heavier braid mono, less for lighter lines) for the main knot 8 half hitches with mono and braid and 6-8 more with out (this tapers the knot off a little.

I used to use double uni/double grinner knots and still have the odd one on spare spools, however I found two issues: 1 - the knot had the tendency to slip on occasion, regardless of how well the knot is tied. 2- with heavy lines to narrow diameter braid the delta in the dimensions would snag in the eyes. I didn't manage to get around issue 1, but issue 2 - have a look at the tapered leader below. For a period this was all i used and it made a massive difference to my casting.

http://www.gerrysfishing.com/daiwa-tournament-tapered-shock-leaders.ir

I havent use the slim beauty - how is it for strength and size Crezz?

the slim beauty is a good knot Greyheads1 and perfectly suited to casting. the braided side if the knot runs through the guides before the mono section of the knot making it slide through quite easy with no clunking or sticking on the guides. quite strong too. I use a modified version where I pass the braid through the double granny (as on the vid) then tighten the mono down. I then just do a uni knot with the braid instead of wrapping the braid up and back. works like a charm.