Wow, thanks! I'll post the 'code'. I am running stock 1.6. Most settings do not matter, but there is one that turns it into a CPU limited scenario for worst case performance: Aerodynamic FX Quality set to Normal instead of Minimal. This cuts FPS in half.
Basically I press space once to engage engines on the runway, press T for SAS, and hold shift for 100% throttle. On takeoff at end of runway I am around 35-40fps. The faster I go, the lower the FPS due to the Aerodynamic effects. Pressing F11 toggles it.
At 300 m/s below 1000m, I am at 18fps. GPU is at 30% usage. Pressing F11 puts it at 31 fps.
If you own it on Steam, you can go to KSP Workshop and search 'Arrowhead 2 SSTO', as thats the same one.
I tried putting the code in a spoiler tag, but the code is far too long. Here it is on Pastebin:
https://pastebin.com/dLqHZQMw
Kinda wish I could just upload the craft.... But basically copy the code, go to installation folder -> saves -> your save -> SPH -> make a plane, save it, and replace the code with what is above. Or use the Workshop. Sorry this wasn't as easy as I hoped....
edit: reason I am so curious is there has not been a proper CPU benchmark for KSP yet. Only user submitted info, with tons of variables. I didn't give you my settings, but I find the only setting that affects my FPS is Aerodynamic FX Quality, even at 4k with 8x AA.
edit 2: If this is too much of a hassle to test, I don't blame you. Didn't want to derail your thread