Gas pipe sizing--summation method Q

I need to add a gas line for a cooktop to my existing natural gas piping. I have been stifled in this because the standard sizing charts indicate that my 3/4" supply is too small right off the bat. However, I understand there is a lot of safety built into the charts and that the summation method can be used to more precisely determine capacity and sizing. I found that on this site, thanks to 4Johnpipe. So, here I am to try and confirm my effort to use summation. If I had 7" WC, I think it would be a no-brainer, but with 6" (as stated on a Vectren Indiana meter application I found online--I am in Clark County, if anyone is checking), there is much less room for play in the figuring. BTW, I am getting some estimates, but I am not sure any of these guys know how to do it this way.

Since it is pretty crowded with ducts and pipes, I was thinking CSST would be the easiest way to add the cooktop line. The big box stores sell a whole kit for 1/2" if I can get away with that size. They also sell 3/4" coils. But, I my brother has the tools and the know-how to do black pipe, too.

In my first run at the calculations--assuming I did it right--it seems doable without replacing any of the existing pipe. I am attaching a diagram that I hope sufficiently shows the situation. I dotted in three possible scenarios for adding the cooktop line. I hope it is legible enough.

Any help is appreciated, especially from John, who seems to be a champion of summation.
Thanks.