Ooook.
1) First off i would recommend visiting your local shop, and try to see if one would fit (hold a flex 7 against your existing pair).
I am not sure as the Flex 7 always appears slightly wider to me, so try before u buy.
2) System X Autocockers... this is my personal views only.
System X Autocockers are not real autocockers, the bodys are basically a replica, there are no WGP serial numbers to be found.
Although they are not real bodies, doesn't mean its going to be any less decent performance wise.
Sys X cockers i have seen lots of trouble with, leaks are the main problem on the 3 way, and the re-cocking pneumatics wear very easily.
Overall they are ok but not worth investing any hard earned money in, in my opinion.
Get an Eclipse Cocker or one that uses original bodies and has a proper company backup.