[Campeador]

Yes, the Star Blazers mod was a learning experience. The Yamato had like 20 weapons and the xfile was huge (2,389kb). But being the star of the game, and just one, it was able to run. The consistent crash was with the BS Conqueror that has 22 weapons, and even thought the xfile was not that big (619kb). There were 8 other ships with bigger xfile size like the “Gas Clod” (5,271kb), the carriers, and even the “Cosmo Zero Fighter” (652kb) was a bigger xfile than the Conqueror, yet it was the Conqueror freezing the game.
So I tend to believe that the problem was excessive number of weapons. By version 1.4 I think that I reduced the amount of weapons on the Conqueror in order to prevent the crash.
On the new mod Multiverse the Yamato will have only 10 weapons, yet it will look like it has 20 weapons. For example I am using a bitmap that will show 3-barrel battery (tree times the damage amount also) but when fire you will see three simultaneous beams. That was accomplish by messing with the BitmapEffects file. So the meanest ship will not have more than 12, and so far no crashes of this nature.
I am also trying to have a ton of fighters on the screen, but now even though I resolved the crash due to weapons, a new crash happens due to Xfile size at once on the screen. To solve this new problem I went back and redid most of the ships, especially the fighters since they are so small that details are hardly seen. Still there is a limit before one really cool crash happens: The ships will still move but the fired missile will be frozen static on the screen, and the laser beams are frozen lines, and the coolest one, damage smoke follows a long none ending line or curve as the ship moves! So there are limits on how many you can put on the screen at once.
Also the amount of stellar objects like clowds and asteroids can slow dow the game.
At least a distinction can be made from the two crashes:
Too many weapons an the game just freezes while ships explode, too many ships and the game slow down and bitmap effects acts really weird!

I am still learning and experimenting, but I hope this insight helps.