Here's a Y88 stripped back showing extra black rear panel and masking pattern. 2-tone Formulas were the same, just in black or gold and extra triangular masking pattern behind bumper to join up with lower stripe paint. I haven't seen any good photos of March '78-onwards Formula / TA 's in other colours but makes sense that any with the black would also have the matching black-outs, to bring in the newer 79 model. Paint coverage is only where needed, even then it is only just!
Note the paint masking uses the angular trunk metal fold. Also, the black over the spoiler end corners. Some gold in the gaps may look bad since not all were perfect gaps. Black with gold Formulas are the perfect opposite, with gold patches there. Regular TA and Formulas may not have this colour change. In fact I don't recall seeing it outside of Y88's and W50 Formulas, although haven't looked too hard either.
Here's some more:
Yellow and Black W50 Formula, same as TA for top half, has small black corner touch ups too:
And a Black and Gold W50 Formula, opposite the Y88 above. Can see they only wanted coverage for trunk top, centre panel and top edges really but a continous paint flow along the back and down onto stripe. Doesn't seem to have the bold masked off top corner patches: