I was told by a driveline shop that you should have 3/4 of an inch slack at ride height out of the seal. If your yoke can bottom out, I suppose 3/4 from bottom is correct. That just ensures that you have maximum yoke to spline contact. I have 2 inches out at ride height now, but my yoke is like 8 inches long. The driveshaft is pro-welded and balanced so I dont want to alter it. If it wobbles, I got another thats 1 inch longer but its not post weld balanced...