Since I myself mod and play on a laptop, I can help here.
Yes, there is a direct corrolation between the model size and crashes, simply put, bc dosnt like large models all too much, and being on a laptop youre more than likley to run into this.
There ARE methods to improve your performance, mainly dumbing down your visual themes for windows to high performance will help GREATLY if your running a newer os than xp.. Wich would be most these days.
Other things like texture sizes play a burden as well, tone them down to medium setting, also dumbung down or turning off nanofx helps as well... Especially the explostionfx. Cut the particle count down to LOW (i run below 50 and they still look great.
Other running programd will affect everything as well.. Simply put, if it dosnt NEED to run.. Close it before booting bc.
Others will tell you the AMOUNT of mutators active affects performance, try duaabling mutators you DONT normally use.. Beware tho.. Some mutators RELY on others.
It all varies from comp to comp, but this should point u in the right direction..
Whats your comp specs and BC install details? (installed mods)