As said above, just raise the forward edge of your stock windshield using one of several methods. I made my own brackets which are invisible, looks factory. I've tried many aftermarket windshields, and have gone back to the factory one mounted at the proper angle. Its not actually backpressure that is the problem, its turbulence flowing off the top, which spills over and shakes the riders. If you are a pilot you understand an aerodynamic stall.
A flat plate mounted parallel to the wind generates litttle drag or turbulence. As the angle of that plate increases the turbulence and drag increase. That turbulence is what you feel, and increasing the size of the windshield does nothing to reduce it. You must reduce the angle of the windshield, and unfortunately the adjuster on the ST1300 increases the angle as it goes up.
I rode an ST1100 for 12 years and tried every windshield there was. By far the best was the Laminar Shield, not only because of the lip on top, but because it was sloped back the farthest. Lower angle of incidence.
The ST1300 brackets I made are triangular but you can accomplish the same thing with a pair of flat plates, with 2 holes about 1" apart. Mount them at the lower forward end of the mount. The ones I made have a slot so I could experiment with different angles, but once I found the right spot I have not adjusted it since, other than moving the power adjuster of course. Others have made similar devices.
