best rear driveline slip joint length

I'm swapping the rear driveline from the factory location to the parking brake output shaft. I'm using a combination of NP202 parking brake parts and a 1310 yoke that bolts to the drum.

The driveshaft in the old position has about 1.5" of length before the shaft bottoms out in the slip yoke and when I connect this in the new parking brake position this distance is down about 3/4" to 1" before it bottoms. Its still plenty of room to get the u-joint into position, but is 3/4"-1" enough to operate safely without ever bottoming the slip joint out?

Any sense if this shaft should be shortened to allow more slip joint room? If so, should I be aiming for 1.5" of slip joint movement?

Also, the rear shaft appears to be an aftermarket replacement, but almost identical to the factory shaft.

Rear axle, transfer case and springs are all 100% stock

Thanks,
Bryce

As the rear compresses it will "shorten" but the rear shackle will go back and counteract some of that...the only way to truly know would be to cycle the suspension...Street truck, I probably wouldn't worry about it, offroad or nonstock springs could cause issues