Is the Kadet Jr similar to the Senorita? If so, it looks like it has a lot of wing for it's weight. Starting with a low wing loading initially is important when adding floats. With floats, mine came out close to 30 ounces per square foot. That means stalling speed is somewhere in the vicinity of 24mph at sea level. Assuming the structure is strong enough, it should make a good float plane. I think a strong .25 would work fine, if that's the largest engine recommended. Don't get too slow on approach, and keep the nose DOWN until you're close enough to either flare or set it down.

Flaps, I dunno. Extra weight for not a lot of benefit, and the added risk of the bird popping off the water before she's really ready to fly. Unless you have a long run of unobstructed beach to fly from, you'll find that the plane will always be far enough away from you that seeing it well and trying to judge accurately what it's doing become difficult. Anything, like flaps, that adds wrinkles will just make it more difficult.

Mine was an arf, and I didn't feel like recovering it for better visibility. I should have. If you haven't covered yours yet, I suggest Coverite neon red on the top and sides(including the fin), and black or very dark blue for the bottom. If you're covering the floats, make their tops and sides neon red, and the bottoms black. The Coverite neon red comes out as an incredibly bright orange and makes it super easy to see even small airplanes. I used this combo on a 40 Shrike, and it really works.

The GP ARF floats I used were intended for a much larger Cub, in the 9.5 pound range. My whole airplane with 3 pound floats only weighs about 8.5 pounds. I think having the floats so big really paid off. It's no aerobat, but the water handling is great with no tendencies to plow under, flip, etc, and if I do a crumby landing it just bounces back up in the air. The ARF floats came with a lower fin assembly that I used to get extra vertical stab area. You might want to consider that and leave your stock fin as is. It was basically a piece of lightened 1/4" balsa, covered. GP had this fancy mounting system that allowed it to be removed from the airplane easily. Just gluing it to the bottom and strengthening it with a couple pieces of triangle stock would work as well.

Make sure to mount your floats so that your CG ends up in the general vicinity of the steps, and mount them so that the bottom of the wing is at 1-2 degrees positive incidence compared to the flat top of the floats. It seems to me that the plane lifts off the water cleaner if the C.G. is at or slightly behind the steps, but I'm not real sure about that. Still playing. I only have about 1 degree positive incidence, and wish I had a little more. (It takes a fair amount of back stick to get my bird off the water. More than I like.)

Water is your enemy. Use rubber gaskets (RTV works good), backed up by a thick layer of Vaseline at the wing saddle, backed up with a layer of colored packing tape over the wing/saddle joint, top and bottom. Use sealed pushrods, or pack the ends of the tubes with vaseline, or both. Before putting control horns on the servos, gob vaseline around the tops of the shafts where they come out of the servo. One drop of water inside a standard servo will make it go whacky. I nearly lost my plane four times due to this. (I've had more good luck than I deserve.)

Hope this helps.

Bob Hunt
Cadillac, MI