I'm serious too. Someone do this and report back.
Here's some extreme autogen results with a clean install of FSX on my i7/Win7 system and no cfg changes or tweaks of any kind. For the test I was running at 4.0GHz. All scenery sliders were maxxxxed out including autogen, with the exception of water at Mid 2.x, and ground scenery shadows off. All AI and traffic was off for the test, cloud draw set to 60mi with medium density and fair weather theme. DX9 was used with bloom off, and multisample AA was used to remove any potential GPU bottleneck at high framerates.
So for the "test" I threw the Acceleration P-51 up, down, and around downtown Chicago with the throttle firewalled, constantly changing directions as well as constantly panning the the camera around the aircraft . Using a 30fps lock it stayed pegged at 30 the entire time, and no blurries despite my best effort to create them.
Unlocked it ran between 35 and 75fps+, not going below 35 at any point, which is impressive for a major urban area and max autogen, though mostly it stayed between 40 and 75. The low points occured during intense panning and turning. So that was with vanilla FSX.
I also tested the same settings only with a tweaked cfg using FTX/REX and the more intensive Orbx weather theme 3 and A2A P-47. With autogen again maxxxed but using MAX_PER_CELL Trees=1700/Buildings=2000 I stayed pegged at my 30fps lock in any rural areas I tried, but when over a giant sea of houses, such as over Brisbane, it would drop down into the low 20's, like 22fps+.
Using 1700 trees with max autogen looks perfect to me with FTX, full yet performant, though 2000 seems a bit much for buildings and large FTX urban spreads. I wish I wasn't getting the herky jerky with the framerate lock turned off, but I've tried everything to eliminate that with the only solution being a framrate lock. Luckily it's fast enough even with the lock.