Go with the sendero light contour to fit in a light varmint barrel channel, you might still need to open it up a bit though.
Take a look at the Wyatt's DBM set up. It's one of the only styles that doesn't have a giant mag release leaver sticking out of the bottom. They do feel a little cheap compared to a lot of other styles though. If you aren't on a budget you can look at the HS Precision DBM assembly. It uses a proprietary magazine (so does the Wyatts) but the the HS bottom metal is very low profile and extremely nice.
You'll love the Nucleus, it's a great action. I have an original Gen 1 and one of the Gen 1.1 versions and I actually like the Gen 1.1 better despite the slightly greater bolt throw. If you haven't ordered a 19# replacement spring yet, you might want to. It makes a huge difference in how the action cycles and I haven't had any issues with the 19# spring in either of my actions. The 16# spring that my original Nucleus shipped with did give me some trouble, but the 19# spring fixed all of those problems.
I'm tempted to grab another of the Gen 1.1 actions while they're still on sale. Looks like they only have .473 bolt faces left, but I could find a use for short action with standard bolt face!
