On Fri, 15 Nov 2013 09:59:08 -0800 (PST), Ivan Vegvary
wrote:

Inherited a bathroom project. Basement, slab floor, shower pan installed (32in x 32 in) already installed but on a slope. It is about 3\8 in. out of level. My odc prevents me from not correcting this even though it does drain. Three options.
1. Pull pan and level concrete slab.

Sounds best

2. Pull pan and carve away on fiberglass ribs.

Weakens the pan

3. Pull pan and shim (possibly roof shingles) floor.

See 1. above

All advice appreciated. Note: There is no shower stall yet. Just pan with surrounding studs. Pan has not been affixed to studs.
Ivan Vegvary

Use good (stainless?) screws when you attach the pan to the studs.
Not those dang drywall screws I've seen done before.