That will not work. The rear rubber bushings have a super tight grip around the bar. They have to be removed then reinstalled. What I would do...
You can remove the bar and then remove the brackets, bushings/resinstall and resest to your ride height or do it all with the bar on the car. Removing the bar sucks unless you do it on a lift.
-Mark the bushings with paint stick or something to make a reference of the OE position.
-Make marks for lateral and radial positions.
-Remove the metal brackets. They are gonna be tough to free from the rubber bushings. swing them side to side while pulling on them. Sometimes it helps to use a flat screwdriver tip or a short pry bar in the bracket holes to kinda pry them side to side. They'll start working off. You don't have much room. But if I recall correctly you can atleast get at the bottom holes.
-The rubber bushings will have a split on their flat area. Spread them here, don't spread more than you have to. They are rubber but have either a metal or plastic core.
-Reinstall at your new ride height. Note that the OE bar has a preload, even at OE ride height. I don't recall which way the bar is preloaded, up or down. It's possible that OE preload may make the bar neutral at your new ride height! You can choose to duplicate this OE preload at your new ride height, but you can only observe the OE amount with an unmodified ride height, obviously. I believe GM adds some preload to add responsivness to the bar.
-When I repositioned the OE mounts on my Gen 5 SS 1LE (same style), I used some hand soap as a lubricant on the bushing to bar surface. This allowed me to easily position the bushing and adjust if nessecary. The Devil's Lube (spit) can also work.
Both will eventually dry and allow the bushing to grip as intended. Let both dry before driving.
-Reinstall the bracket. The fasteners are 43 lbs/ft.
There's alot going on with the OE rear bar. Not only do they have an overall preload but a slight twist too, which then adds more (or less depending on perspective). The super grippy mounts add a slight amount of overall rate.
The front bar just has a little preload, a slight twist in the bar. But the front bushing is actually glued to the bar! I half-heartedly attempted to remove the bushings from my front bar once but felt it wasn't worth the squeeze just to understand it further.
When we install aftermarket bars with their lubed poly bushings, there is no grip on the bar.
EDIT: I see your sig says LT1. My observations have been with the SS 1LE, ZL1, ZLE. I believe your LT1 does have the grippy mounts but the OE preloads, if any, may be different.