Max Distance/Slope for Under-Slab Wet Vent

[djm284]

I'm a non-plumber roughing-in DWV for a new bathroom in my basement. Wet venting everything through the sink vent/drain. For venting the toilet, I'm having trouble interpreting from the code if, for a given slope, there is a maximum length between the wye labelled 'A' in the picture below and point 'C' where the wet vent will go vertical, or is there only a maximum length between the toilet and point 'A'?

Right now the slope between A and C is 1/2 in per ft. and the length is a little over 6 ft. I can adjust the slope down to 1/4 in per ft if needed.

 

[hj]

It is more complicated than necessary, but should work.