Tips isn't terrible on clay, but his (attacking) groundies aren't really reliable enough for the longer rallies. Thus he's not rated too highly on the stuff.

That's clay as an average. However, Hamburg the ball really flies since they changed things around in 2009 (new balls, warmer part of the year), and attacking players can do quite well now. See the final's since: Davydenko-Mathieu, Melzer-Golubev. These are all aggressive players, not unlike Tips himself.

For Tipsarevic, you basically need to know how quick the clay is - on the slower stuff he's awful, and often just gives up. Altitude clay, Roland Garros, new Hamburg, maybe Rome, and Barcelona some years - these are all much better for him.

Lines don't tend to take the subtleties of courtspeed into account much though. On clay it's quite important, especially when it rains they become dog slow, and all the dynamics change completely.