http://www.gamesas.com/user/666599-realmeleven/ - I had the same issue on a couple of my homes. Resolved it the same way. Think I posted that fix in a thread last week. Full LOD does not seem to work on objects that already have LOD attached to them in some way. It is sort of trial and error, but you can almost guess which objects need it and which don't after time.
Also, if your machine can handle it, set ugrids to 7 in your Skyrim.ini. This will lessen the chance of your new location fading into view. It might load before you ever see it. Keep in mind that changing ugrids will affect all of your saves. Do Not Argue has batch files you can run to fix this, but it's something to keep in mind.
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Thank you http://www.gamesas.com/user/517940-eldiabs/, for the suggestions. When I'm placing something in more open country this will be very helpful.
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Where I have the tower located (just up off "Riverwood Path"), it is obscured by trees, rocks and buildings before coming into view. From Whiterun, it is concealed by the eastern shoulder of the mountain (at the eastern extreme of the range bounding the north shore of Lake Ilinalta). From Riverwood village, it does not pop into view until the line of sight is less cluttered. Not absolutely perfect, but much better than my previous attempts at positioning large models out in the open. Finding a suitable spot in rugged country with limited line of sight can hide a multitude LOD sins.
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However, when I move on to bigger and more frustrating plug-ins, the higher ugrids setting could be useful - so thanks again.