I have seen a number of posts on the Limbsaver for the Nova but thought it might be helpful to organize what we know in a single post as well as offer my own review of the system.
To begin with, when purchasing the limbsaver for the Nova make sure that you buy the correct pad. I recommend checking the templates first in case there are any changes to the product, but I can also tell you that the current Model 10401 fits Nova. If you buy the wrong product you are going to be SOL. I bought mine at BassPro for $50 including tax (a bit expensive but cheaper than the hard to fine comfortech pad from benelli).
Limbsaver does not give very good instructions on how to install the pad but it is relatively simple. Remove the stock recoil pad by simply pulling it off. Insert the plastic frame into the stock. This will likely take some time as you have to fiddle with it quite a bit to make it fit right (be careful with the plastic frame, it seems pretty durable but you wouldn’t want to break it). Next, simply place the pad over the frame and use the screws provided to attach it. Make sure you screw it down pretty tight to ensure a good fit.
Compared to the BPS and 870 I actually think the nova has some of the worst felt recoil. I have yet to try the supernova or the recoil system. While shooting 3.5” inch shells I found it almost unbearable and more than 250 rounds per day with sporting clays or skeet left my shoulder a bit sore (2.75” 1 1/8 ounce). For me, I have felt a noticeable reduction in recoil felt when using the limbsaver. It is hard for me to quantify how much of a reduction there is, but I can say that I don’t grimace as much when shooting the 3.5” and 3” are extremely easy to handle. Moreover, I do not have even an inkling of sorness after a long day shooting 2.75”. I would recommend it for anyone looking to tame the nova a bit. One word of caution, the pad does extend the LOP quite a bit and if you are sensitive to that I would recommend going a different route.
Hope this helps and happy shooting.