I guess I'd ask "how much leakage?". If you have the hole on the inside of the collar open and flowing to the rocker shafts so you can see oil dribble out of each weep hole on the rockers themselves, there shouldn't be a need to further crimp/seal that tube.
On the flip side, if you're not getting oil weeping from each of the rockers under regular pressure, or very little (knowing that you've already checked the rockers for obstructions), then you could further crimp it to try and force more oil through the rocker shafts.
