JT,
That explains a few things.
I was interested in your fuel CG comments. As I figure it, you leave out the 50 IU number to get the formula for the fuel line, otherwise you don't get the right numbers.
It is interesting to see that the calculated fuel CGs are fairly close to those stated in CAP696.
Main tanks 650.7 as against 650.66
Centre tank 600.4 as against 600.14
Full tanks 628.8 as against 628.56
I assume that the differences are due to rounding off of the IU values in the trim sheet fuel table ?
Your comment about not using the full tank CG values for the long hand calculations becomes a little clearer when the CGs are calculated for the fuel table. I calculate CGs varying from 610 (empty) inches moving back to 650.7 inches (full main tanks) and then moving forward to 628.8 (full tanks).