Lowered shocks

[LordDevlin]

I'm trying to figure out another situation I'm having with my truck as I work through all the issues of a new old vehicle, especially one that has had some mods.

that being said, when I get up to about 50 miles an hour or so and hit a bump, the back end of the truck seems to really bounce hard and I almost hit my head on the roof. The axle has been flipped and there are two leaves back there, with all new spring perches and everything.. the p.o. had a shop to all the work and it looks good. Not sure if the springs are posies, and I recently read someone else having the same issue of bouncing hard with the posies in the rear. I do not have a notch, and I know some of you will tell me I must have one, but it seems as though there hasn't been an issue of bottoming out at all with the way they have it set up. Could this crazy bounce be from the rubber bump stop hitting the axle and then somehow creating this rear end bounce? The truck is down for a day or so while I iron out a loose front end but when its back on the road I will mark the bump stops to see if they mark the axle.

This got me into to looking at lowered shocks. I was surprised to see that the nitro slammers that everyone refers to for lowered applications are the same travel as the regular ones for these trucks, about 12.5 to 20.5 inches. I was expecting that they would be same travel but from some a much shorter compressed length.

Can someone explain to me what makes a lowered shock a lowered shock? Do they somehow take into account that your default starting point is less than half of the travel or something?

Thanks for your time.