Have a look on your chart for Sarn Badrig, bit of a sail for you but most fish can be caught off there. Macks will be anywhere there is water in summer, I find that once I get forty foot under the keel I start to get them regularly. Can't help with specifics as I fish the other side of the Llyn.
Try prospecting along the low water mark up from Borth-y-Gest. I've not seen much caught usng bait on the bottom but schoolies come close and are catchable on plugs and spinners. Fished there 'on holiday' from the midlands even though I'm from the Menai Straits. The point on the seaward side of the harbour at Borth-y-Gest features in a North Wales fishing video. Mike Flynn caught lots of species there although haven't had the luck myself!
BUT .... I've seen, but not yet caught, (did you catch the 'not yet'?) some trully enormous Mullet seen feeding (and laughing at my attempts) off the two main promintories. Ate bread/groundbait but not with a hook in it! A local angler fishes for little else, using the aforementioned but mostly little white rag. The deep water point next to the Powder House (below Morfa Bychan Golf Course) looks incredibly fishy but beware the predatory Jetski and mass herds of 4X4s i've seen doing a 'churning' ritual there!