I'm confused. From what I've read, all you seem to be doing is boosting the lower frequencies of the current mix by however many decibels (3 I think).

That's not a LFE track. LFE is low frequency effects, not just the low frequencies louder. Many people already have their home theaters configured so that frequencies below a certain number of Hz gets routed to their subwoofer.

This is because a lot of the F/R/RS/LS/C speakers in home theater setups don't have good articulation of the low frequencies and the subwoofer is asked to do the job of a normal woofer. (That is, LFE does not equal Subwoofer). Don't get me wrong, there's nothing wrong with this since bass is largely non-directional.

True LFE are frequencies usually below 40-50Hz (though they can start as high as 80-120Hz for smoother transition from the other speakers frequencies). The audio tracks you are working with should not contain frequencies this low because home equipment is not expected to be able to articulate it. (I haven't checked, the laserdisc PCM data MAY contain frequencies this low, but I wouldn't count on it.)

Your current method is only overdriving the current normal low frequencies. You can do this at home by going into your tuner and increasing the volume of your subwoofer relative to the rest of your speakers. (Some subwoofers even have a separate volume knob right on them.)

In fact, your current method runs the risk of causing clipping (volumes so louder the peaks are flattened and crappy sounding).

The best way to do make an LFE track would probably be to strip the LFE track from the official 5.1 mix and sync it to the mix you'd like to use.

Another idea, while it's more theoretical at this point, would be to find frequencies below 80-100hz, and copy them to a new track then pitch-shift them down about 25Hz.

I don't know how it would sound, but it's an interesting idea.

Otherwise, I'd strongly recommend against your method.