Negative Lag time issue with notifications

Hi,
We have our projects set up with negative lag time for all tasks, since we need to work off of a certain Launch or Send date. Now we run into the issue, that the assignees of e.g. Task 2 do not get notified anymore, since the predecessor in the list starts on e.g. Task 1 Predecessor = Task2 - 5days. Any ideas how we can have a proper workback form a Launch date where all tasks lead up to, but the notifications will still work?