After starting my homemade surf gate project, I realized quickly that the swim platform would need to be modified for a few reasons. The beauty of a teak platform is that it is more easily modified for surfing!! Plus it always looks great refinished.
1) The gates need to retract/close all the way in at an angle, or they "drag" in the water and tarnish the wake. I watched this occur many time while surfing with our test gates.
2) The wave itself runs right through the platform, I think is why many manufacturers, even without gates, have cut the corners on the platform to follow a better low speed, surf wake line.
But because I needed to fit the gates, it was a no brainer.
On this particular project I actually added length to the original swim platform. So it is one board length longer. Teak is actually very easy to work with, as long as you have a good skill saw blade and cut slowly.
The angles were determined by watching the wake, and honestly just by how far the gates needed to retract into the platform. I will come back and add to this project with the steps involved.
It's also important to look at the bottom corners of the gates to ensure they don't run through the wake when stowed/closed. Some with SG have had success without modifying the platform, while others have had issues (like me).