to me it seems strange. it should feedback less because it has a powerfuller sound, so you would need to dial less gain... but the opposite also stands right, as this has more volume. just try using less gain control and rise the level of your amp/monitor if you need it (but with less gain).

as carbon fiber is so resonant, i also faced this problem with the cargo, specially with lower notes. 

Feedback often seems to show up in the low end. I wonder if the huge body of the JM1000 isn't contributing to feedback by providing a big low end. On the other hand, because it's so loud, it might just be because it's putting a hotter signal into the mic. Maybe just step back from the mic a bit.

I have found all my CA's feed back way more than woodies.  The big body on my Legacy feeds back like a mother on the lower frequencys.  I just wrote someone about Cargo feedback.  Hope this helps.

It looked like your Cargo was not Gloss finish so my vinyl pickguard idea wont stick to it.  But find some black art paper or the poster cardboard stuff at the art stores or Wal Mart and cut a piece a little larger than the hole in your Cargo.  You will have to hold it on with some scotch tape in a couple places.  Shouldnt look too bad.  I just tried it on my Cargo to get rid of the feedback and I was sitting in front of the amp.  Also it will clean up the overall sound nicely.
Hope this helps.  Walt