Vertical drain drop from toilet

I'm installing two back-to-back toto drake toilets and have been told by toto technical staff that they may not work properly with my 50 year old opposed cast iron tee. A double combination wye was suggested.

Can I come directly from the closet flange to the wye with a 1/8th bend at the closet flange?

I read in one place on-line, Plumber's Handbook, that even below a toilet, the max vertical drop is 24 inches, just like a sink trap.

I know a 45 degree wye is not a vertical drop, but it is not a 90 degree, either. Is this code? Will I violate code, or have plumbing issues if I go straight to the 4 inch stack with the 45 combo wye?

toilets

The first thing to understand is that if you use a Y and 1/8 bend, double Y and two eighth bends, or a double combination Y-1/8 bend, your toilet opening(s) is/are going to be a lot more than 12" from the wall. You need a double fixture fitting that is similar to a double combo, but narrower so it does set the toilets at the proper distance.