Good to have you with us.
Recently, some of us did a deep dive into this device here which you might find useful.
As I understand the only issue here is having two parallel negatives. I wonder if that’s because no two speakers have the same ohms, leading to two competing waveforms, which damages the amp on the return. 
I THINK that means you could run two or more speakers in series providing the load is appropriate. That is the sum of the ohms of the speakers in your caravan. Only one waveform. The M38 shouldn’t be able to tell the difference between two 4ohm speakers and one 8ohm speaker… I think… 
I’d love someone else to weigh in here to make sure I’m not missing something. 
Pix 
