Well, there's one simple way to go. Take the ratio from the sixth gear, activate 7th and set it to that ratio. So for example if 6th gear was set to "58" in GP4 on a well-working setup that is what you should set your 7th gear as well. Afterwards just use regular steps between the rest of the gears. With 7 gears you might want to eventually lower first gear by 1 or 2 steps as well.
So, here's an example how to transform the 6-gear-layout to a 7-gear-layout using the guidelines mentioned above:
Your first gear is set to 26, your final (6th) gear is 58. Those steps between will be set in regular steps, so the whole gearbox-setup might look like this:
1: 26
2: 32
3: 38
4: 44
5: 51
6: 58
Now, adding 7th gear is about giving you the advantage of keeping revs in the optimum (high) range for more time throughout a lap. So you just keep first and final gear as they were but you can now set up the gears in between closer to each other:
1: 26
2: 31
3: 36
4: 41
5: 46
6: 52
7: 58
You can also use the 7-speed gearbox to gain an advantage in the exit of slow corners by lowering first and second gear ratio. But then again, just put the gears in between to regular steps.
If you have a 6-gear layout that works fine for you, substract first gear from 6th gear and divide it by 6 (i.e. 58 - 26 = 32; 32 / 6 = 5,333). The result gives you an idea about how big those steps will have to be (with it being 5,333 your basic steps will be 5, some gears need a step of "6" though which you should rather set the high gears to as you don't want to compromise acceleration out of corners).
Hope this helps, just keep them coming if there's anything left you want to know!
kind regards
chris
Edited 1 time(s). Last edit at 06/02/2011 11:10AM by ChrisJ.