The diameter of the bar isn't the important number, it's the effective rate. The shape/material and the distance between body mount - end link will affect this so just using diameter doesn't tell the whole story.
The posted data is that the rear bar is P1 = 36 N/mm (205 lbs/in) +409%, P2 = 45 N/mm (257 lbs/in) +514% which equates to the new bar is 4 to 5 times stiffer than OE. The front on the other hand is P1 = 26 N/mm (148 lbs/in) +264 %, P2 = 30 N/mm (171 lbs/in) +305 % which is 2.6 to 3 times stiffer.
So from this data it appears you could set the rear on the inner hole and the front on the outer to get closer to the original understeer balance (400% rear 300% front over stock) or move the rear to the inner and front to the outer (500% rear 264% front) to remove as much of the understeer as these will allow.
For something like auto crossing, you should finish braking -before- you turn in and then power out of the turn to use the FWD to help pull the car where you want it to go. Driving like this, you want to try to make the rear tires do a lot more of the cornering work (the front tires have the extra traction load of putting power down plus the weight shifts rearward on acceleration) and is why you want to use a stiff rear bar and a soft front one. This is a less effective way to get around turns as the corner speed increases as you will be in a higher gear with less acceleration. If the car has a hotter motor, it is even more important to take some of the corner load off the front tires. That said, this type setup might work badly on high speed corners where you hold a steady throttle and just "drive smoothly through it" as the car will tend to oversteer which would not be good..
The problem with setting up a car like this for the street becomes, if you go into a corner too hot and are braking too far into the turn (which happens if you don't know the road really well), the rear tires don't have enough down force (braking transfers weight to the front tires) to gave decent grip, the rear tires then lose traction and the back end of the car comes around. This is NOT the same as oversteer with a rear wheel drive car where you can give the car opposite lock steering and power out of it. Doing that will result in a nasty wreck (been there done that). The only way to save it at this point is to apply LOTS of power and hope there is enough front traction to get through the turn. That is a very unnatural reaction and this explains why for safety some understeer on a front wheel drive car is a good idea for most people. There are a lot of compromises that must be made finding the right balance.
