The reason it's not working is because a flat turn at 80 degrees with 0 lateral G's will require 5.75 G vertical force, which is about 1.5 G too intense to be safe if it's sustained. To get a flat turn, type "arccos (1/[your Gforce here]) in degrees" into Google, and use that result for your banking. For example, if you wanted a 4.2G turn, you would type "arccos (1/4.2) in degrees" and Google will give you 76.22 degrees. That means that, if you want a flat turn at 4.2G, you need 76.22 degrees of banking. Of course, that isn't all you need to do. You first need to use some trial and error and random timezone-changing to get the track flat just as the banking gets to that value, and that can be pretty time-consuming.