I can see the extra weight in the line added distance to the cast, it is in effect a more streamlined weight than a weight of lead so maybe a slightly smaller more streamlined lead could be used as well. I find it impossible to calculate all the forces involved so I would have to experiment first if I tried it, maybe cut the fly line down as well. It wouldn't surprise me it could add a bit of distance but the problem of thick line being pushed by the current mentioned by Rubio would mean a heavier main weight to hold it once cast so that would be a problem, some fierce currents exist around our shores. Then there is the problem of that sort of line on a reel a multiplier especially; will it come off the reel problematically? I find using a thinner line means a lighter weight is needed, I can cast a long way with a carp rod and a two oz weight with a 12lb line. The 2oz weight holds bottom well enough just about where I fish but if I used a 25lb line it would need at least a 4oz weight. The wind and current has quite a dramatic effect on line thickness because there is so much of it out there and a thick fly line would feel a lot of that effect in my minds eye.
However, if you have seen it used and working to advantage by others then the proof is in the pudding as they say. I don't think I will bother though, casting long distances is not the be all and end all of beach fishing or pier fishing. There are occasions were that bit of extra distance might get more fish say a far off gulley or rock mark but it is not often. Piers and jetties often hold more fish straight down were the pylons attract crabs and small fry that attract other fish. Fish come closer into the shore than a lot people think as well, bass can just require water to cover their backs, I have caught flatfish on the stones and mackerel will beach themselves on occasions they come that close. Depends what fish are about though. The cod and whiting can be further out but I don't cast far usually, then again I cant say I have caught much lately!!
I remember a first class angler who won a lot of beach competitions who said being a distance caster gave him an advantage sometimes, his bait would be just a bit further out than other competitors who were average casters and if the cod or whiting were swimming that just bit further out he would win the comp usually but he attributed his success more to always digging his own fresh bait and having lots of it.
Still, I would try it if I were you, scratch the itch, some old fly lines can sometimes be found cheap, give them a go, if I find one I might try it out myself sometime.
