The best way is from the rod holder as you mention, but you will need to beef up the gunnel and add a backing plate along with a swivel rod holder to do this safely and correctly, also have a HD rope attached to a cleat and the reel. You also need to make sure your rods are bent butts if using a swivel holder, a straight butt will not work naerly as well and could possibly fail. I rocket launcher is better on the boby then fighting stand up, but is no match for a giant unless you have yougn guns onboard, you cannot move well and the rod tip is placed in the boat, a bad position for it, you want it ver a gunnel pointed putwards at all times to rpevent the line from hitting the gunnel or catching on a cleat. You also want to make sure the location of the swivel holder is where you can fight a fish while following also, since this is going to be easiest for you rather then backing down with outboards. You might want to add a rod holder between the stock locations for the best position for fighting a fish, following while fighting, and then in forward with the fish trailing when getting ready to land it, this would be the ideal rod location for a swivel holder on your boat and for your fighting style. I would fight a giant stand up beforte I would use a rocket launcher, and a fighting chair is not an option on your boat. a fighting chair would be second best, but is not perfered since you need to sue your whole body weight to make it effective and can beat you up on a giant. For your size boat, stand up and swivel rod holder are the only good choices, but if you go stand up you need a lot of really well fit guys and guy belts and back harnesses to even consider doing that, I recommend landing a few from a holder first before you take that task on.
Thw swivel holder is the most productive method and reliable, but takes much of the fun out of catching the fish, to do this though you need to be fishing 150-200lb leader with 150-200lb hollowcore backing. If you use heavy 200lb straight mono you will not have enough capacioty, a giant can burn off a lot of line and quick and might spool you before you even get the other lines cleared to start to follow the fish, and using lighter line will keep you from taking full advantage of applying great drag pressures. Typically you do not want to exceed 1/4 of the lines rated capacity at strike, and at max, about 1/3 of the lines rating, you can go a little higher but now your flirting with disaster. Fighting from a rod holder means strike drags of maybe 30lbs, meaning 120 is the lightest you can go, but some crews fish upwards of 40lbs of drag from the holder, meaing 160lbs at strike to be safe, making 200lb test the best choice for an 80, some commercial guys who use rod holders fish even 300. You will need a harpoon, and keep the transom clear. Fishing giants takes patience and a crew you trust and who works well together. Troll less rods, 5 would be max for giants on a sailfish IMHO, 1 WWWWWWB down the middle, 2 off planers deep and 2 WWWB off riggers. I would highly recommend calling up Joe Shute (
http://www.captjoes.com/)and getting some of his lure's, they are great on giants and the best boats off MHC pull them. Get his 3 oz lures, the 3 oz I believe are $15, cheaper then an islander with better hair and a lot more flash. His lantern's were also hot this past season, so add a few of them as well. Crystal hair with a red head was hot last season, as well as pink hair and pink head, pink/crystal hair and pink head, blue/white combo's, and for low light conditions, purple/black combo's. A lot of boats will troll 1/3-1/2 of the spool of an 80 out, but being that you will have a tougher time backing down then an inboard would, and will need to spin the boat, I would not exceed 1/3. We had a big one on this season for about 2 hours before popping the hook near the boat, and we fished about 300+yards back and were down to maybe 100yards before we got the boat spun and my crew was quick to act.
Best advice I have is have a game plan, make sure everyone knows their job or responsibility, know who is bringing what rods in to clear them and where stuff is to be stored or where your gear is for landing the fish. Keep the deck open and clear and stay calm and confident. Have a few pair of good heavy duty gloves on board, fishing from the holder will require you to often have one guy handlining the line in and one guy on the reel to turn a big fishes head and start to gain on him, and near the boat you will surely need a guy handlining the leader and last few yards. I highly recommend a good harpoon, much better choice then a fly gaff, much easier to throw into a fish then pull back at you, and you typically have more reach with a harpoon then fly gaff, this can make the difference of landing and loosing a fish at the boat. Fly gaff's are better then nothing, but not the choice of commercial boats for good reason. Be consistent once you mark fish, keep going back over the spot, they will come up over time, might take a few passes. I highly recommend using flouro leaders, they do make a difference, Giants are line shy when the bite is slow, which it often is. A little trick is to sometimes pull back the throttles on mark's, or slightly ahea dof them, let the lure's flutter down, and then get back to troll speed and have the lures surge to the surface, I've had many 150-200lb class bft get dupped on that trick, and I know some guys down south that do it as well with great luck, that is where I learned it.
