Lets look at some quick physics. Lets say the average boat on this site is 2000 pounds. The average horsepower is about 700 and climbing. Now, the prop is the single and sole propulsion of the boat. And every single ounce of energy to send the boat forward at the average speed on this page, which would be around 90 mph, is held by one little slim piece of aluminum. You can take that piece of aluminum between two blocks and stand on it and bend it. It is not that stout. Now look at the flex it could get if you put 2000 pounds on it with 700 horsepower of thrust. It will flex. No doubt. Too much flex can mis-allign gears and cause them to break, wear, etc. Can hurt the case, and can make the prop slip forward enough to hit the strut.
Any method of making the v-drive plate flex less and disperse the energy propelling the boat forward to other spots on the boat is a good thing. The angle is nice. But an adjustable 4-link type of deal is better as it is adjustable.
http://www.buzzzmiller.com/vbrace1.jpg
http://www.buzzzmiller.com/vbrace3.jpg
Here are some ideas