You're numbers aren't quite right - the cast is measured to where the fly lands whereas the carry concerns only the fly line. Therefore if it is assumed Nick is using a 10ft leader then the figures are as follows:
60ft carry - 93ft cast, end of fly line at ~83ft -- shooting 38%
65ft carry - 99ft cast, end of fly line at ~89ft -- shooting 37%
70ft carry - 110ft cast, end of fly line at ~ 100ft -- shooting 43%
These figures represent the relaxed style that Nick employed as such the figures are quite a bit lower than the ones I reported in my FPs linked to in post #32. Here I was seeing shoots typically in the 50-60% and some higher, but I (and Tracy) was trying to maximise things.
If you can't shoot a minimum of 40% as per Nick's figures or 50+% when going for it, I'd suggest that your carry isn't perhaps as good or as controlled as you think.
James