Does your device take frequency setting of "auto"? If it does, this is the new default on all devices supporting it. If not, I'd go to official frequency setting (which is 800MHz).
Regarding upgrading to v7: v7 comes with newer linux kernel, which has some architectural changes with regard to routing, and those mean liwer routing capacity. Also beware that v7 can use slightly more flash than v6, and 16MB is a tight fit. If you're not missing any of v7 features, then there's no reason for you to upgrade to v7, you better stay on v6, AFAIK it's safe (for now).
No Auto setting so I've moved it back to 800mhz. Decided to give RouterOS7 a shot and the upgrade was uneventful and everything seems to be working fine.
The only thing I have noticed is that on somedays my signal quality will get pretty awful with SINR dropping to 0 db when it normal is in the 16-23db range. Rebooting the RBLHGGR seems to fix the issue