First tme site user needs help determining the best way to make a level pad underneath a basement floor toilet.
The old existing toilet was mounted on a 4" cast iron pipe (so the pipe shoulder was actually a 5" opening). The toilet had a ton of plumbers putty instead of a wax ring. I stuck a small section of 4" PVC in the shoulder and filled the gap between the iron pipe and the PVC with construction adhesive. I think it will work. It will now take a standard wax ring.
The concrete floor where the toilet sits is un-level by about a half inch from front to back. I think the original installation using the ton of plumbers putty is what made the toilet level before.
My question is: Can I just use something like Quikrete Vinyl Patch to make a level base for the toilet around the waste pipe? Will that kind of pad be strong enough - being only 1/2" thick at the most (1/8" at the least) and laid on top of old concrete?

I am sure you'd like to meet the last guy who installed that toilet or poured that floor. You toilet must be level and shims are out of the question for 1/2". You can use the Quikrete but add the lquid bonder to the mix, same aisle as the concrete bags.

I am sure you'd like to meet the last guy who installed that toilet or poured that floor.

You are right about that! There are a bunch of questions I would like to ask about this old house.

The instructions on the Vinyl Patch say not to use any additives - I think there is already a bonding agent in the mix. I will probably try and make the pad today. I have a little laser light level that might work for getting it even. I'm thinking that if I mark a boundary, and then just pile up some of the mixed patching compound and then trowel it down until I can't see the red line any more - it should produce a flat and level surface.

Thanks for your help!
LennyG

Some bonding cement does say that you should not add anything so follow their instructions. A few vinyl patch mixes I have seen as that you seal the old concrete with their primer to increase the attachment power. Always follow the instruction for the product you bought. Your leveling approach sounds goo, I sometimes just go by eye or feel.