I encourage folks to stop using depth alone as a proxy for how aero something is going to be. It's bullshit logic. The first-order aero variables should be frontal area reduction and flow attachment. Flow attachment depends on the shape (size and relative dimensions) and the surface. Depth is just one variable when thinking about shape, so it's a third-order variable. Yes, depth is influential when shape and rim width are relatively consistent, but assuming that is the case is no longer safe.
The reason we see a lot of wheel clusters in terms of performance isn't due to depth alone. Once you have achieved a laminar flow condition, the system's efficiency will not change significantly. The marginal gains from going from a 50mm wheel to a 60mm wheel should be similar to the performance envelope of most 50mm and 60mm wheels. Most data shows this, but people tend to overlook it because of how the charts are presented. What tends to be different is the yaw angle at which you see the flow transition from laminar to turbulent.
A good front wheel, IMO, needs to more effectively manage flow over a wider range of yaws while a good rear is more aerodynamically efficient across a smaller range. This isn't just about marginal aero gains. If the designers do their job right, they are also trying to manage the center of pressure of the system when the flow does detach, reducing the effect of the turbulent flows on the front end. I've looked at the new Rovals now and I think that the shape of the rear is designed for low yaw performance, and the reason it's not deeper is that accounting for the higher yaw angles the front sees, they don't care much about the flow once the front has detached. This is not significantly different from the logic used by Enve when examining the mismatch between front and rear in their SES range, and how they differ in both depth and shape. What is different is that Roval thinks their tradeoff, given the current trend in rim construction, will result in a lighter rear wheel than Enve's at a similar performance level.
Aside from closely matching the profiles, attempting to compose a reverse mullet from generic rim shapes is likely to be an unpleasant experience for most people.
