The issue with operating at max isn't normally an aerodynamic one, it's more often than not a thrust available issue.
Hence, MCT thrust selected on the N1 page.
If you get a temp change of plus fifteen or twenty degrees while banked at 15degrees you'll be leaving your flight level with the stick shaker going.
As for bank, LNAV calculates safe bank angles that doesn't exceed thrust available. If using HDG select, bank angle selector is set to 10,
routinely, when reaching cruise altitude... again
pr. Boeing recommendation
High Altitude Maneuvering (automatic pdf download)
If you operate the aircraft as Boeing recommends, you do not need to add your own personal margins. Common sense should of course prevail, you do get weather charts in your briefing package don't you? And you do study those charts during your briefing I hope? 15-20 deg temperature change should be something you notice...
Then again I am not the one to report moderate turbulence as soon as we hit light chops.