Wouldn't bother with the seals just get a new cylinders - cheap enough.
Might be worth looking into a different bore size while your at it depending on what size drums you have! Its all to do with the rears locking up before the front and causing you too spin (IVA Fail).
I'm assuming there that your not using some sort of pressure reducer for the rears.
Probably confused the hell out of you there but go for new cylinders
