Currently there is no other way to do that apart from the CSS hack - could you please let me know what exactly didn't work with it? It would be of help if you post a code for a sample page where you tried that hack along with the browser's details.
The problem with the hack is that it sets a fixed height of the dropdowns, no matter if there are 2 or 200 items in it. That is actually one of the reasons why currently there is no permanent cross-browser's solution for this issue.
All the best,
the Telerik team
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Public Issue Tracking
system and vote to affect the priority of the items