That is actually a really good idea.
And they said I was mad...
Would taking the hi level signal to a hi level input on a sub change the load on the speaker and alter the output??
Speaker is 8 ohms maximum, amplifier input is at least 10,000 ohms, probably 47,000 ohms
There will be no discernible drop in level on the drive unit (if it did, the sub would do this to a passive pair of speakers in it's normal operating mode).
I thought routing the cable out of the port would be the easiest (no drilling) and easily reversible. I'd assume the drive units share the same space as the port so attaching to the bottom one would also be easy.
Good Luck!!
Steve.