Keep in Mind...
Depending on where you are in the world, the season, etc., you can get your XXX kicked trying to top thunderstorms. It's safe to assume that ANY thunderstorm can give you a bad case of heartburn with as little as 5000 feet above the tops of the clouds. And, consider crossing the Rockies in the spring or fall....you get a fast-moving front with the associated squall line....and you can get severe turbulence up to 8000 to 10,000 feet above the tops. (Yes, this is not theory...it's actually happened!!!)
So, it's true, unless you're an SR-71, it's better to simply go around 'em. It's a nice academic exercise to calculate the tops using the RADAR tilt. Keep in mind, tropical thinderstorms have tops that paint a lot better than early-spring boomers over the Rockies. (They're relatively 'dry'.)
Fly safe,
PantLoad