Tom Petty did indeed specify a wider neck for his signature Rickenbacker 12-string, but his isn't the most obvious example of its kind and not the one most players would pick in terms of classic styling.
As you say, Lionel, the standard Ricky narrow neck width is fine for those blessed with Susannah Hoffs' size, dinky digits. Unfortunately, my fat fingers need a lot more room to move, which is why I find the Double 6 ideal. The latest Chinese-made model is excellent too and ensures that I don't miss the '60s examples I've parted with in the past. The 12-saddle bridge is a vast improvement and the extra pickup selections are a bonus. Just to improve appearances, I've fitted modern repro Burns knobs and switch tip, while my stock of original spares supplied the correct, much bigger headstock badge. With these replacements installed the instrument now looks as good as it sounds and the 'D' tuning delivers loads of low end grunt to go with classic ringing chime.