Sorry to burst your bubble.  BobMullike has a very good description of the difference between C3 and C4. It has everything to do with what happens at the cellular level. 

If you look at where corn - maize - is native, it is central America: Mexico and south.  Corn is grown in much of the northern US due to man's manipulation of the genetic code, creating hybrids that can be grown much further north.

And for the record,  corn - maize - is corn in the USA. In much of the rest of the world, it is Maize.  And, in some areas, if you asked for "corn", you would get a C3 plant - wheat.  So, just be careful where you toss around that term - corn.  :)

C3.5..... no, I don't think that is going to be acceptable.  It's either C3 or C4 plants.  No transsexual plants in the maize family.    :)

edit: I'll toss in a thought here, and this is my personal suspicion... no research to back it up.... if you are looking at the drought tolerance we currently see in milo and they compare it to corn/ maize, and wonder why corn/maize does not seem to have as much drought tolerance..... I'd suspect it was bred out when man starting monkeying around with the gene pool.  The drought tolerance was one of the things that got lost in the pursuit of higher yields.  Again, that's my suspicion only.