Thinking about making a go at the Dunn Westbay late this summer and am looking for some legistical beta. I've done plenty of aiding (desert mostly), done a few grade V's (fishers), but never anything quite like the diamond. Do you have to sleep on the wall? How many nights for a slow party? Is a portaledge necessary? Are the Casem view rappels the best way to approach? If so where would I find the beta for those?
Sounds like you are up for an adventure. I would recommend coming out to Estes and spending a bit of time on Longs and the Diamond before tackling your objective. Maybe climb Chasm View wall to the North Face as a recon outing, then the Casual or Pervertical on the D. Then you will be better able to answer those questions for yourself.
Personally, I think that sleeping on the Diamond, while possible, is not advisable in the height of summer. We have significant thunderstorms with lightning, hail, and cold temps most afternoons. You are best served to pick a day where the weather.gov point forecast for the 12999 foot level is a low percentage chance of storms (like 10% or 20%) after a late hour, like 4pm, and climb in a day.
It is also a damn long way to haul a proper wall kit.
I prefer to approach the D via the North Chimney, which, though a bit loose, can be pitched out, simuled, or soloed more quickly than hiking up to Chasm View and doing the raps. The raps also tend to create a lot of rockfall which may put parties below at risk.