Photoshop :: How To Integrate Speed Grade Into Workflow

I love Photoshop CS6, and my absolute favorite new feature is the Color Lookup adjustment layer. So far, I've been extremely happy with the effects I've been able to pull off by combining that with other adjustment layers, channel work, etc.
 
However, I've gotten to the point where I realize that my next step -- much like a user who graduates up from using actions he/she downloads off of Deviant Art -- is to make my own color look up tables. The only tool at my disposal for this is Speed Grade. (I have a CS6 cloud membership -- off topic, but way to go, Adobe, that made it feasible for me to "graduate" from only having Photoshop CS5.1 to having the full suite at a very reasonable price!)
 
I've used Speed Grade on video clips I've shot with my Canon 5D MkII to great effect. Nothing I'd post publicly yet (I'm still learning how to shoot motion), but I considered the results to be very positive. I've managed to save several test .look files, as well, both on video footage and still images (JPGs, to be specific).
 
I always shoot RAW, and my usual workflow is to start in Aperture (I'm a Mac user), do some basic RAW adjustments, then export a 16-bit PSD and get down to the real work in Photoshop. SpeedGrade doesn't yet seem to support PSDs natively, so in order to create a .look which is appropriate for my image, it currently looks like I need to export a JPG (down to 8-bit sRGB, ugh) from Photoshop, then open THAT in SpeedGrade, do my work, save my .look, go BACK into Photoshop, and use the .look file there.
 
I could live with that if -- IF -- the .look file actually gave me my expected results. However, the only time the .look behaves exactly the same in Photoshop as it does in SpeedGrade seems to be if I open the image as a JPG -- thus losing all my layers, adjustments, smart objects, etc. When I apply any of my .look files to a PSD, they come entirely too dark, every time. Many of them have simply turned an image into a large 22 megapixel black rectangle.
 
So my question is this: How do I make a SpeedGrade .look file behave predictably in Photoshop, in a 16-bit-per-channel PSD file? I'm OK with changing the color space if I have to (even if it's to sRGB, the bane of my existence) -- but I need to see the same thing in SG that I do in PS. Is this possible today, or am I waiting on the next SG release? Or, and I assume this to be the case -- as I'm a software engineer by trade, and know that this is almost always the case! -- is this a case of user error? And if so, what can I do to correct my user error?
 
Or, sacrilegious as it may seem since I have all of Adobe's tools, are there other Mac-based products I can use to create color look up files compatible with Photoshop?
 
In case it matters, here's my platform:
 
Canon 5D MkII, latest firmware, always shoot RAWApple Aperture 3.2.3. Mac OS 10.7 (late 2011 MacBook Pro 17", 16 GB RAM)Adobe Creative Suite 6 Cloud Subscription (photo, illustration, video tools installed; no Flash nor web tools)