I fish a 19' Custom Weld. I had a custom "roll bar" type thing welded up, it goes up and over the canvas, I have one plastic tube mounted vertically on the outside starboard side to hold the net vertically, and two on the port side mounted at an angle to hold two rods & reels. I have four other plastic tubes at the back of the boat to hold other rods & reels. I usually run three Scotty downriggers.
I bought the boat used, and it came with four swivel pedestal seats. I removed the rear two, replaced the starboard one with a 150qt cooler, and bought some bench seat "seconds" from the Custom Weld factory when I was there. Had a friend weld up an aluminum box to fit under the bench seat, made it a sort of "couch" on the port side. The people sitting on the cooler or the couch have to face the center of the boat, but I can fit two people on each if I have to.
I keep all my tackle in the hard plastic "Plano" style boxes, and have a soft bag that fits maybe six of the big ones. I keep all my flashers pre-tied to spoons and hootchies in the X-Stream style flasher bags... I have four or five of those, couldn't live without them. Most of the time I'll keep one bag tied up with an assortment of sizes of terminal gear, for exploring if I don't know what's going to work, then each of the other bags contains gear of a similar size, so once I zero in on the "hatch" I just sitck with different colors and styles from the one bag.
I bought one of those open toolboxes, the kind that is plastic and just a handle with a tray around it, no lid or anything (hard to describe), I keep all my round halibut weights and such in that, and use the 1qt Tupperware containers as dividers within this box, for the smaller weights.
I use long (4'-5') lines on my downrigger release clips, and keep at least two hook-out dowels, (one on each side of the boat) to use to unhook unwanted fish, and to grab the release clip lines, so I don't have to lean over the side of the boat to get them.
I keep the downrigger balls (15lb) in the gunwales in the rear of the boat, they stay there and don't roll around. The gunwales towards the rear also carry the Smelly Jelly, a rag or two, knives, WD-40, hook files, etc. The gaff hook, oars, rear light, and stuff that isn't used that often are stuffed in the upper parts of the gunwales. The gunwales forward, under the canvas have the rags, paper towels, maybe some drinks, batteries, flashlights, stuff that doesn't neccessarily like to get wet.
I like using the plastic "Plano" type boxes because I can organize my gear for what style fishing I'm doing, and either only bring what I need, or only have the boxes out that I need. The uneeded ones stay under the seat or in the soft takle bag. One box will have plugs, one will have mootching stuff (herring helmets, etc.), one will have extra spoons, etc., then I have smaller ones for swivels, extra downrigger crimps and hardware, that sort of stuff.
Boy, you're making me think of what a mess I have in the basement right now, I need to get some stuff organized!
-N.