Have a look at this thread, I put up a lot more detail.
more details here:http://www.akff.net/forum/viewtopic.php ... 0&start=15
1. the waterproof chart card slot in my Elite 5: I first fitted the card then cut out a neat cover of (strong outdoor weatherproofing tape Bear brand) I think it is for windscreen repairs. Covered the card slot, then pushed the cap back over. But I also ended up running a thin bead of silicone sealer just round the edge of the plug cap. I can peel this off again if I need to get the card out, but it will stop water sitting around the inner edge of the cap. I did this round all the outer edge seal area of my Elite 5 and it has screws holding the back on so they got a thin bead of sealer. I figure that I am never going to need to pull it apart so might as well make it as well sealed as possible.
I will also have a little wetsuit cover for the sounder to keep the slpashes off and cover the screen when not in use. (see the other therad for a photo)
2. I did try the DSI transducer in the hull but the wet mount I had made for another transducer allowed bubbles in. So I thought I would try this idea first.
Tonystott has managed to fit the transducer up neater into the scupper hole using the Lorwrance kit. But as you say it is prety expensive.
3. I agree about the cable set up not being ideal. This is why I used the boat bung plug fittings. I figure that I will always have some sounder or other electrical gear so, to change over or remove, I can simply unscrew and change electrics when I ever get a new unit without having to drill new holes.
I have cut the DSI cable and re-joined with a Bulgin mini waterproof connector. http://www.bulgin.co.uk/Products/Buccan ... rMini.html
But if you do this you MUST be really neat in how the cable end insulation and shielding is done or it can reduce signal quality.
Have a look at the other thread and see the through hull fitting that Tony has used (you do not need to cut the cable for this).