Bill Smythe, I agree with you regarding surveys. I’ve done several of them, the actual turnout in events is often quite different from what people SAY they want to play in.
Now let’s have real fun
We decide to rate G/25 5" delay as dual. Do we now require score keeping too?
Now for yet another way to look at this 
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Our club wanted to give our players three different kinds of rated tournaments: quick-rated only, dual rated, and regular-rated only.
The longest time control we could use for a quick-rated event was G/29 delay 3. We can fit five rounds of that into a 9-to-5 Saturday (can still do date night with the significant other!). The only up side to making the games shorter is getting home earlier. Anyone see other up-sides to shorter games?
We started with the objective of running a quick-rated event, and worked from there. We saw a value to providing tournaments that are quick-rated only.
If it is clear (from the TLA wording, or from whatever rule is in effect at the time) that the event is regular-rated, then yes, you would have to require scorekeeping.
(I assume Steve Immitt requires scorekeeping in his weeknight 4-round events.)
Concerning dual ratings: Keep in mind that a dual-rated event is nothing more than a regular-rated event (using regular-rated rules, such as scorekeeping) that happens to also be quick-rated.
Bill Smythe
For many players, especially in relatively fast controls, the lack of a scorekeeping requirement could be a big up-side.
So for your quick-rated event, you wanted the slowest possible (G/29, d/3). For the regular-only event, I assume you’d want the fastest possible (G/61, d/5). What would you choose for the dual-rated? G/45, d/5? Or maybe you could try both extremes – G/30, d5 and G/60, d/5. (Now you’d have four kinds of tournaments to compare. Good luck in running enough of each type to be able to conclude anything from the numbers of players who show up. 
)
Bill Smythe
Please see the “House Rules” thread in the “All Things Chess” forum.
Alex Relyea