Maybe try Tywyn at low tide say halfway along the prom - aim for the gutter that runs in front of the reef that runs parallel to the prom and only appears on big LW Springs. Use rag, peeler, sandeel. Might get a bass if the nets ain't in place but it does give a few flatties anyway! If you do try it you'll have to be able to tolerate a bit of weed giving false bites, because of the lateral currents. In the wrong conditions this can mean getting 1cwt of it round your line, so you'll need to keep an open mind on the mark - same applies to the Estuary when the tide's running hard especially if the waterskiers etc have liberated even more weed from their holdfasts on the sea-bed!
Nefyn I know nowt about but some of us lads from here are going to try it this summer!
Cheers - John