I have a house built in 1962. The cast iron waste pipe runs under the concrete slab in the basement. I have already dug and confirmed the location I want to cut a section out of the pipe and install a "Y" connector and run new plastic waste pipes to a new bath. I have seen PVC connectors that would connect plastic to Iron, but I am concerned that it could create a hump in that area (cast iron to PVC and then back to cast iron). I have also seen saddles but those seem to only be used for clay pipe. What is the best way to do this so I do not risk a clogged waste pipe. Thanks!

I have a house built in 1962. The cast iron waste pipe runs under the concrete slab in the basement. I have already dug and confirmed the location I want to cut a section out of the pipe and install a "Y" connector and run new plastic waste pipes to a new bath. I have seen PVC connectors that would connect plastic to Iron, but I am concerned that it could create a hump in that area (cast iron to PVC and then back to cast iron). I have also seen saddles but those seem to only be used for clay pipe. What is the best way to do this so I do not risk a clogged waste pipe. Thanks!!
Since you failed to gived us the size of the cast iron main I'll assume it's 4".
How I would go about this conversion would be to purchase a 4" PVC Street Wye and prime and glue in a short piece of PVC into the wyes hub. This will give you two bald ends to connect the cast iron to. Fernco. 300 Series (Fernco, Inc. (http://www.fernco.com/proflex.asp)) Has shielded couplings,(see image) that will fit cast iron to PVC.
Rent a set of cast iron ratchet cutters, (not snap cutters) and measure from one end of the wye to the other. Make your cut 1/4" over the overall measure. When you install the wye give the branch of the wye a quarter bubble on your level for slope. Good luck, Tom