There are times when three waying eels out off block when you need lots of weight to hold bottom, the trick is to let the sinker hit bottom then reel in a couple of cranks and drift, the tension of the water will prevent the eel from curling up on the leader, as for three waying at anchor, I have never heard of it, three waying is synonomus with fishing a drift just like drifting for fluke. I would cast and retrieve at anchor but not just let the eel sit there on the bottom. When I fish currents like in our breachways I add rubbercore sinkers to the line to get thye eel down more but other than that I still fish them the same way.
I know guys who fish the race and sometimes need 13 ounces of lead just to get down and stay down in a good moon tide rip!
Alot of guys I am hearing from are now just using an egg sinker above a good sampo swivel instead of the three way rig, when a bass picks up the eel it does not feel the weight and they say this is working out great!
I also got the tip on the orvis mirage flouro from these boat guys they say it makes a ton of difference and now that I use it for leaders I have to agree its great stuff and really takes a beating, I use the 60lb orvis mirage and my leader is long at about 8 or 9 feet, it can really take a pounding in the rocks, give it a try.
But boat fishing aint my thing
so I am no one to ask! Just my opinion!