Dornoch Firth is good for flatties. Never lost any tackle there either. Ardjachie Point is a good spot that i normally fish.
Around Invergordon as well. Normally catch flatties and sea trout there.
If you do fish around the area can you send me a report on where you went and what sort of ground it was like? I am trying to build up a little database for people to use of marks around Scotland. Click the link in my sig to see what i am trying to do.