So I've been wondering a lot about this myself, I just ordered up all my stuff yesterday, and I decided to go with the DS303's and the stud top adapters. My primary goal is to make the suspension work really well, not necessarily be super low. I mean I don't want huge gaps either, but If the 303's with the stud top don't get me low enough, I'll go to thinner body mounts and or spindles and try to maintain the most shock/wheel travel I can.
The main difference I can see between the stud top mount and the pro-comp adapter is that while the pro comp adapter is hard mounted to the shock hoop, the upper shock eyelet can still pivot on the adapter itself, while also pivoting on your mounts as well. Versus using the stud top mount on the shock itself, which takes that upper pivot point away. The thing is, I don't know if there really needs to be any pivoting/deflection in the upper mount for the shock to survive. As the LCA moves through its arc and the shock lengthens and shortens, is it sufficient to have the only bottom shock mount swiveling? I know the OEM solution has the fixed upper mount, but that probably has some pretty squishy rubber isolating it, and more importantly it's not bearing the weight of the whole vehicle. On the flip side, the stock Tundra suspension looks a lot like what Atomic has created, and from the pics I can find it is using a fixed upper mount for the coilovers as well. Which makes me think ours could work with a fixed mount too. Also looks like MacPherson struts use a fixed upper mount as well. Just food for thought I guess... I'm pretty sure a solid upper mount would work, I just don't know if I want to risk $320 in shocks to find out, lol.