Uh on, 56K'ers beware, Last Chance is typing again!
Don't use any of the "Mix and Fill" epoxy filler crap, it will proabably just fall off in the area you plan to use it. Epoxys can be tougher to work with because you must use fiberglass cloth with no starch in it (called E-Cloth). They also don't "stick" very well when wet, you will be doing this repair upside down. Normally, whe using polester resing (Standard Fiberglass resin)the rather stiff cloth, roving or mat or whatever you use will seem to "melt" when you put the resin on it, this is because the resin contains styrene, which dissolves the starch in the glass making it nice and flexible. Epoxy doesn't have styrene, hance it does not have that nice smell you get when you catalyze resin. Although epoxy will have a much stronger bond (It sticks to fiberlgass better then fiberglass), you will have fun getting your final coat to stick to it, and there is usually lots of sanding between coats because of "amine blush". If you don't want to worry about finishing the final product, epoxy may be stronger IF DONE CORRECTLY, but far from necessary in the area you want to fix. Remember, Epoxy is about 100 bux a litre for the good stuff, about 100 dollars worth of abrasives, brushes, E-Cloth, solvents and mixing crap, then your time to do it. Plus, Epoxy goes downhillvery quickly when exposed to sunlight, which will be an issue over time on a trailer boat.
If using polyester resin, get the stuff from Industrial Plastics, or the Marine Supply Store in Duncan. Get Un-Waxed, unlike the stuff from Canadian Tire, un-waxed is what you need when putting mulitiple coats on. It dries to a tacky finish, but promotes bonding by other polyester based resins (Being more fiberglass, or gelcoat).
You can just sand the area well, build up with layers of glass matt (The stuff that looks like hair pressed into a sheet) untill the shape is what you want. Cloth is not what you want here because it will just peel off if the edge is not finished correctly. If you are just fixing where the keel meets the transom, just build it up to where you want, remembering to overlap the edges up onto the transom a little, and try to terminate your patches at the inboard strakes if they are close to your work (I don't know how far back they go on an Eagle). If you use a flatboard parallel with the bottom of your hull, you can make it nice and flush and flat.
Before starting to work, cut several sheets of mat a little larger then the area you are going to patch. Make sure you sand the area clean, I reccommend using a sander instead of a grinder cause you can "pop through" quite quickly with a 10,000 RPM grinder. Mix the resin a little "hot" (5% MEKP instead of the usual 2%), and apply your patches, you should be able to put 3 layers a time on, and with that much catalyst, do several shots in a day. Just wait untill your previous work is firm but still tacky, and re-apply. Don't let it get too hot (If it smokes, you are doing it wrong LOL). Dont' forget to roll out the bubbles with your roller, with a small patch, dabbing the cloth with the end of your brush may suffice, you will know you have no air in it when you can't see the cloth, it will just look like resin.
Fair the area smooth with short-strand fiberglass filler, and 80 grid sandpaper. You can get a litre of gelcoat for $20, and if you are lucky, Industrial Plastics can even "sort of" colour match it for you, I wouldn't hold my breath on that one when matching with old gelcoat. Simply roll on the gelcoat, get a nice thick coat, then sand smooth with 150 grit. One smooth, work your way down from 300 to 1000 grit paper while wet-sanding. Get a good buffer, some good compound, then some good wax and buff it. Voila! It is important to have the area fair will the hull, because if your gelcoat cracks, you could "peel" your repair off if not done right.
Or, 400 bux may sound good right about now to protect your investment, I will bet you spend almost half of that buying the things you need to to it correctly (Sandpaper is even expensive!). Having done some glass work myself, I really REALLY would need a good reason to do it myself when the dust settles, and the itching stops unless I am doing a full-blown restructuring in a nice warm shop with VERY GOOD breathing gear.