Don, there's safe and there's comfortable/fun. On my CD-22, for salmon I think 3 is the ideal number - 3 rods out the back, one on each corner and one out the center. One guy drives, one guy reels and one guy nets. I can and have fished with 4, but it's a bit tight. Especially on the way out as there's really only seating for 3 inside the cabin. For bottom fishing on a CD-22, it would depend on the weather and what we're going for. Calm weather and rock fish, we'd be at a dead drift and then 3 is again the ideal number as that's the number of rods that can comfortably fish out the back. If I were to fish for halibut, we'd typically be backing into the wind/current to keep the lines on the bottom and then we could take 4. One to drive and 3 to fish at any one time.
On the CD-25 the cockpit is a good bit larger but I think you'd be hard pressed to comfortably fish any more than 4 out of the back when bottom fishing and 5 when trolling. Remember, when you're halibut fishing, you're usually in deep water (200-400') so you have a lot of line out. Also, the weather/seas are invariably pretty crappy during the short halibut season we get around here. So you will typically be backing into current/wind. That can bring water over the transom on occasion so you want one or more LARGE bilge pumps for this kind of fishing. Also, if you put a bunch of heavy guys at the aft end of the cockpit, the problem is compounded (in some cases the scuppers can even be below the water line if the guys are really heavy). So if you're planning your first halibut trip in the 25, I'd start out with you + 3 others. That way you can see how the boat handles under the typical halibut fishing conditions without being anywhere close to being overloaded.
Finally, be careful out there. Halibut fishing in small boats is one of the most dangerous activities that boaters take part in out here in the NW. Unfortunately, the halibut season in the ocean is typically in April/May and maybe a few days in June. The weather is usually pretty nasty during that time with seas of 6-12' being common. Rarely do you have swells of less than 4' and rarely do you have winds less than 15kts. Of all the available days for halibut fishing in WA, I would say that about 15-20% of them are nice in the ocean. A portion of what's driving the setting of the season is driven by fish biology (there are more halibut in the Strait of Juan de fuca in early spring than later in the year, especially in the east end). However, another driver is to try to spread fishing effort out during the year to provide more economic benefit to cities on the coast. That's why we in WA see seasons with odd things like a Thurs and Saturday opening - e.g. so you have to stay 3 days to fish 2. Given the short and spotty season, people often go out even when the weather and seas are awful. If you're backing into waves, things can go bad in a hurry so wear those PFD's and make sure you have good bilge pumps (pumps - plural). Most of all, if the weather is too bad, stay in port. It's really not that much fun to fish in nasty weather anyway and you can always buy halibut if you really want some.
Just my two cents worth.
