Personally, I have no hands-on/real world experience with shallow mount sub woofers, however, there are lots of basic mechanical/acoustic/mathematics at work in a sub woofer system. Emphasis on system because there are so many elements involved in building an effective sub.Has anyone installed shallow mount sub's in there ridge line..what are the pros and cons if any
There's more pro than con when it comes to shallow mount sub drivers. Here's why: by definition, this type of driver is designed for limited air space inside an enclosure that will fit behind the rear seat of an RL. In that regard, they have mechanical attributes maximizing their performance in small enclosures. *IF* there is a down side to a shallow sub driver, it is "limited" X_MAX which is the specification defining cone excursion. The rough analogy of X_MAX in an internal combustion engine would be stroke of the crank/piston combo. A short stroke by itself might be considered a limiting factor, but there is more at play than that single design element. For example, short stroke of a piston can be compensated for by diameter. So a larger diameter short stroke woofer would be a good thing if it is installed in a properly sized/designed enclosure. I can't say for certain but I'm thinking a 10" is going to be the max diameter for what I suspect you have in mind.
If discussed as a single part of a long list of sub woofer attributes, "short" X_MAX could be perceived as a negative but that is much to simplistic a view of how a component within a system works. A woofer in a box is WAY more than a woofer in a box.
One of the things making sub driver selection "easy" in this category is: there are fewer OEMs playing in this consumer space. So the limited selection makes choice pretty basic. If you are like me, price plays a big role in which driver to choose, and pricing runs from cheap to not-so-cheap. With that in mind, find the driver in your price range, look at enclosure specifications and build an enclosure within those parameters that'll fit the space you have in mind. Easy-peasy.
Here's a couple of examples of whats out there: