Slip yoke supposed to slide all the way into the transmission output?

I had a driveshaft built according to measurement for my 400 trans. When the rear universal joint is bolted to the pinion flange, the slip yoke could actually slide in another 2 inches into the trans. The builder tells me this is normal. Could someone help me out here.

 

so, what do ya'll know? Is this going to ruin my new transmission?

 

Sounds normal to me, it needs to be able to move into and out of the trans for the diff. to move and not bottom out inside the trans.
I ran one that the driveshaft was too long and it was hard to get the u-joint in the yoke. I'd say if you have 2" in the trans past the seal it is OK.