Suffice to say I don't do my bracing like that any more!
I should take that old video down....it's embarrassing!
As the discussion in the video's comment section says, I agree that there's nothing parabolic about any of the curves....perhaps they should be called parabollocks curves?
I got "caught up" in the marketing hyperbole, sorry.
My "internal heel" idea is still alive (just) and I may revisit the idea later this year. I have continued to do experiments of all kinds with new materials and building techniques. Looking for my niche in the market I guess....
E.g. my all-spruce triple-top with strat-like arm relief curve experiments seems to be working out - I have a couple more experimental guitars in the pipeline with improvements (thanks to some useful suggestions from other builders and players) - stay tuned.
Cheers,
Dave Fifield