I wish my flat bottom turned as sharp as a V but they usually don't. Some people like putting a whale tale (hydrofoil) on them for faster lift out of the hole and some stability, but you would get more stability in turns from trim tabs. Stainless props don't flex like aluminum do but in your application I wouldn't stress using either one, the racers like them because they don't flex and give like aluminum will so they get a little more boost from them. The down side is when you bang a SS prop it can cause damage in the gearcase where an aluminum will take the damage and 'ding' up .
Porposing is caused by a hook in the hull, usually near the back from improper trailering. Once you get up and move on top of the water the hook catches and lifts the nose, then it drops, then it catches again and up it goes and so on. It is easily casued by people not supporting the transome on the trailer but letting it hang off the bunks, with a motor on it. As you drive and bounce it the bottom of the hull flexes until it developes a hook from side to side. Not something you want.
Finding the proper pitch prop usually takes a little trial and error, find the manufacturer's top RPM range for that engine, run it without a full load to get a prop that sets you up on the top end of your top RPM range, that way when you are loaded it will run still in that upper range.