With careful placement of struts and fuel tanks in a very specific order i managed to reduce the total part count to 690, but it still lags horribly on my old 2,66 GHz i5 (about 2 fps). I think the strut count is around 90 , luckily they are almost infinitly strong when placed correctly ! I launched manually without any physics tweaks or any mods , luckily the rocket is surprisingly stable and reliable, the launch took almost an hour though ... I got a gtx 660 , so it shouldnt lag this much , maybe im running out of memory ? (i got 8 GB)