the last BRS I worked with which was a 750 .,, I'm thinking it was 14 lbs,..so weighing that much you want it as close to the CG mark as possible,..

As for using BRS systems,..personally I can't see the use unless your planning on doing some serious aerobatic maneuvers that far exceed the G rating for the plane,..and remembering that listed G load's are not max ratings,..max ratings are ussually 1/2 again the listed G rating,..that's a 9 G ultimate for a sustained 6 G rated aircraft .. gross at 1200 =7200lbs sustained or 10800lb ultimate,.. I don't think the kitfox can go fast enough with any normally asperated engine on it to reach a 9 G ultimate load unless your over loading it to begin with,..just my personal feelings of using a BRS,..
Kitfox's are built way to strong to ever need a BRS,..as long as your not over loading it in the first place,..
but like I said ,..that's my personal feelings concerning the issue

Chase