So I’ve had the same Seastream for a while, I think I have the first blue camo one they ever shipped. I agree it is a great kayak, very stable, and it moves through the water nicely. A couple of things I wish they would change.
Agree they should have a cup holder molded it. I bought a heavy weight cup holder and I have Velcro on either side of the seat, where the cup holder attaches. I too slid Plano boxes under the seat, it I absolutely hate the strap holding the seat being in the middle of the kayak. I really wish they would find another way to attach the seat and leave more room for standing with tripping over that strap. Little boxes go too far back under the seat and bigger ones do not fit because of the center strap. I like the Vibe Shearwater system and wish the inside of the SS was similar. I eventually put a Plano 3600 in my crate which solved some of the storage issues, but you have to turn around which is inconvenient.
The rudder control is fine but the cables need constant adjustment to keep them tight. I too use a Scotty mount for my fish finder and yes the track needs adapters to use just about any brand, they should change the track system. What I really hate most of all is the extra flooring they put in. It has slots along the side so water can drain, but the slots are big enough for lures ( mostly soft plastic, and Crappie lures) to slide under also. In addition sand and gravel goes under too. And don’t drop food in case it slides under, it gets stuck and then rots and stinks. The only way to resolve is to remove the extra flooring. But to do that you can never get the screws lined up again, because they are just randomly drilled into the body of the kayak, so you end up with a ton of silicone and extra holes in the floor of the kayak. Worst design ever! I ended up snaking 1/4” poly tubing around the edge of the floorboard to minimize the problems.
In the end I would still keep the SS over other brands, but there are a few things I hope they change.
George