NewNitro, that could be due to a couple different things,
The springs might be a bit stronger than your previous setup. The stronger the springs the more revs needed before it will hook up. When it does it tends to hook up hard.
Most three shoe setups have different holes to mount the shoes onto the flywheel. That can also affect hook up.
Finally, if you put the shoes on backwards it will tend to grab quick once it engages. Whan the shoes are on the right way it will slip a little before it actually grabs.