it sounds like you have a small problem with configuration naming.
what is wrong with the standard elbows that SolidWorks gave you?
How about doing a save as to you custom folder to an existing elbow that solidworks likes and then deleting all the configs that you do not want to see.
So there isn't much wrong with the standard elbows, however I am trying to create a custom library of PVC parts to have accurate pipe lengths (as the radius is slightly different for PVC elbows). I also want to be able to drag in any part, whether it's an elbow or tee or union, and have it auto-size to the route through the part's various configurations, which should also allow me to have accurate prices and information for a BOM depending on the diameter of the pipe.
Is your solution simply to overwrite the existing files with my versions? So far I have just been saving the files into sub-folders I made in the routing library. My hope was to avoid overwriting the existing files, and just add to the library.
do a save as of the elbows. Then modify them to fit you pvc dimensions. This may cure the problem you have with the elbows not wanting to come in right. I would go with a socket weld elbow and from there modify the part and the materials to match the dims of the pvc parts that you want.
Look at doing a design table for updating the part.
Remember that if you add a blank row after the last part that you want that is where the table will stop. You can use this to keep the other configs in the table but not have them update.
Have you searched 3dcontent central for any pvc fittings. It would seem to me that someone may have already created everything that you are looking to do and there should be a zip file somewhere that you should be able to down load like we could do with the weldments.