i've done the same fighting wolf did with the 50 mollys. There were 4 players in the system with me (1 with me in bedford space. i was in a rh bs. the rest were in the same system but not with us), and arround 12 players online.
There was no lag at all.
The las due to thruster might be caused by your video card. Or maybe you have a p2p client uploading stuff at max bandwidth? That will cause severe lag...
Also, engine and wing trails cause no lag at all as they are calculated client side..
(If you find any mistake in my English, please let me know via a PM)
(Really, I speak terrible English, so please, tell me if I make mistakes. I'd like to improve it a bit )