Hi Poncin and welcome to the forum. We have a Mirage Tandem that is a couple of years older than yours. It also leaks a little, mostly through the hatch mount aft of the back seat. That area gets a lot of water washing across and it tends to sit there. You would also expect some water to enter through the rear cable openings. Actually, all three of our boats take on some water. BTW, it's good to sponge out the water after each use and open the hatches to let everything dry out.
None of the Tandems were involved in the Retrofit.. In fact, the longer bolts may even be too long for yours. In any event, I'd recommend that you leave it as is.
The sand colored cracks were almost exclusively Outbacks. Sand also happpened to be the most popular color (at least then), so they had more cracks develop. Whether there was more to it than that I don't know.
The best thing to do is just use the boat and enjoy it. Keep an eye on things, learn how to lube and adjust your drives. That way, if any problems develop you'll be right on top of it.
Congratulations on your purchase!
