theyre fine on the track, no where near the oil control problems of the rb26, but like any car fit a bigger sump and baffle for the extra piece of mind.The under steer issue can be fixed one of 2 ways, either upgrade the rear sway bar and leave the front one but to me that a compromise as you are taking away rear grip to compensate for the front not having enough.
I believe the better way to do it is to fit a front lsd, which gives the front more grip and doesn't take any away from the rear