Shower drain install

I am having a problem leveling a shower drain installed in slab. The tub was removed to install a stall shower. A new p-trap was connected to the riser from where the Oatey drain will be. The main drain is 24 inches from where the shower drain will be, and approx.12 inches below the slab. There is approx. an 8-10 inch drop or down slope from the Oatey drain that connects to the vertical riser, then to the p-trap and then slopes to the main drain. This causes the vertical riser to be about 1/2 inch out of plumb.
I have tried to wedge pieces of the slab I broke out to hold it, but there was too much resistance. The vertical riser is approx. 7-8 inches from where it connects to the p-trap to the top of the slab. I have been thinking that I need to dig out the pipes, cut it off at the main drain, put in a 45 ell to decrease the slope and reinstall the assembly of riser, p-trap and straight, sloping drain to get closer to the 1/4 inch per foot.
Any ideas would be greatly appreciated.
revbob

OK, I dug out the sand fill around the pipes and enlarged the hole in the slab. I am now able to flex the pipes enough to bring it into plumb, but it takes about 30 lbs of pushing.It flexes from the elbow at the connection to the main drain to the p-trap and the vertical riser. I tried putting a 25 lb dumbell over the p-trap to hold it down, but that wasn't quite enough. I can hold it in position with a 2x4 braced against the head wall until I back fill.
I have two concerns:
1) I don't know if the backfill alone will hold it in position and
2) Will the pressure of the flexing cause the joints/connections to eventually fail/crack/leak?
revbob

drain

Unfortunately, your descsription of the installation does not help us visualize it. Is the lateral pipe from the tee to the P trap the one that has 8"10" slope? If so, that is not only your problem but also improper.

Hi hj; Yes, if I am understanding you correctly. Starting at the Oatey, the 2 inch pipe descends, 14 inches to the p-trap, it then goes laterally (sloping horizontal) 14 inches with a slope of 1 1/2 inches from the p-trap outlet to an ell that connects to the tee of the effluent(out) drain. I dug it back out, repositioned it and braced it until I can secure it in place with some concrete.
revbob