WARNING.
I cannot recommnd using minecarts at all, since of entity limit issues.

Minecart tracks count legally as walls for rooms, laserbeams fire through minecart tracks.

So you can use minecarts to transport a lot of stuff into a room, avoiding logistic grommets.
(and the bloody mess of trying to get more belts in).
And/Or fire a laser beam right through tracks, avoiding energy grommets.