Anyone know what the percent Of grade is the For the over and under figure 8 kit
If the piers are placed as shown on the box it's 5.6%. That should put your locomotive's pulling power down to about 10% of what it will pull on the level.
Pier sets are intended to maked a figure-8 'over and under' layout fit on a 4 x 8 plywood table top. Without worrying about how practical the grades involved are. Even the Atlas set, with 46 piers, ends up with a grade around 3.5%, which is considered pretty steep by most people who have been around the hobby for a while.
With the EZ-Track piers, you can improve the slope of the grade by using two sets of piers. Measure the height difference between two adjacent piers in one set. Divide the difference in height by two and write down the result. Now make enough shims equal in thickness to the distance you wrote down, or as close to it as you can get, to put under the second set of piers. You don't need a shim for the starting wedge piece of the second set, as it will not be used.
Start at the low end when place the piers under the track with the starting wedge and first unshimmed pier. Then alternate, using the first shimmed pier, then the next unshimmed pier, and so on. You should end up with piers starting near the 9" straight at the bottom of the figure-8 up to the 9" straight at the top. This will bring the grade down to a bit over 3.5%
The only way to get a smaller grade on a 4 x 8 is switch to N-scale and use Woodland scenics 2% foam risers. To get a shallower grade in HO, you need a bigger table.
Len