Dan if you already have wire truss strut setup (I thought you were attaching the floats to the existing main gear and adding a second to the rear.

If the trainer has a flat bottom you mearly position the floats fore and aft and that will be where you use the landing gear straps to anchor the two struts accross the bottom. Inside the fuselage at these two points glue two plywood plates accross the bottom and that will give an anchor point for the langings gear straps.

The purpose of the float bows in front of the propellor is to help prevent noseovers Landing, Takeoff and when taxiing downwind. This usually works out pretty good if you size your float length to about 3/4 of the fuselage length but not always as there are some airplanes that just don,t fit the formula. Its not locked in stone and I have flown some that the bows did not quite make it out to the propellor but of course required carefull operation on the water.