I suspect the low perfomance issue isnt in any way due to high poly count or low end PCs, but directly linked to poor LOD architecture
First, there's no "low performance issue" at KLAX, there are only some users with either outdated systems, or new system but badly configured.
See (and read carefully) this message for proof:
http://forum.avsim.net/topic/353381-cloud9-klax/page__view__findpost__p__2160184Swoop had a very fast system, but his 1GB card under XP 32 bit was the bottleneck, once he upgraded to Win7x64, everything changed, and KLAX started to perform as it was supposed to.
In any case, saying that the problem is not the high-polygon count but the "poor LOD architecture" is self-counterdicting: the LOD IS a way to display less polygons, when the full resolution model has too many of them so, the two are strictly related and, in fact, are the same thing.
And...LOD can be tweaked without re-modelling evreything
No, it can't in this case, which is entirely different.
KLAX for FS9 doesn't have a "poor LOD architecture", it doesn't have ANY LOD at all, for a very simple reason: BECAUSE of the already too high polygonal count, we were so close to the maximum limit that FS9 can handle (32k polygons per drawcall), which is lower than FSX anyway, that putting LOD levels in the objects would result in the FS9 compiler not compiling them anymore, and even by hand-tweaking it to bypass the limit, FS9 wouldn't display the object anyway.
We already *had* the LOD levels, from FSX, but we had to throw away them in FS9 in order to be able to compile the scenery.
Now, before you start jumping "that's it, it's the missing LOD!", the true story, as always, is not so simple.
Modern graphic cards are so fast and with so much *spare* power left when using Flight Sim (and especially FS9), that simply putting a lot of polygons without any LOD could be FASTER than the very act of *switching* between LODs, since there's some computation that affects the CPU involved when deciding which LOD level display based on the object size so, with a fast modern system, this overhead is worse than just drawing *everything* in one go, since the calculations must be made for every object and on every frame.
LOD is very helpful with slower systems, OR systems with less powerful graphic cards OR systems where (like Swoop's) the graphic card was underperforming because of the memory issues in 32 bit.
So, I repeat and confirm: KLAX for FS9 performs normally on a correctly configured fast system. If you have a old PC, there's always the Cloud9 version, which is still on sale and still supported.