We are aware of this problem. Basically, the correct approach depends on the concrete scenario. That is why, I cannot tell you whether you can achieve the result you want, unless I examine your code.
On a side note, because of cases like yours, we have made major refactoring of the coercing mechanism in RadTimeline and RadTimeBar. You can test your code with the latest internal build to see if it fixes your problem as well. The fix will also be part of Q2 2013.