heres the low down on spacers [ and a little on tire profile ]
adding spacers to just the front will lower understeer, hence giving more oversteer
adding spacers to just rear will reduse, and possibly iliminate oversteer [ in most situations ]
adding them to both front and rear as a whole makes the car more stable. and still keeps the stock [ or close to stock ] response.
the problum that you ran into with the tires could souly be based on the profile and width of the tire. [ along with tire pressure ]
when you have a lower profile and a wider tred the tire is stiffer all over. [ sidewall AND tread-patch ] this means that you have a greatly reduced "slip-angle"
[ this means that the tire dosnt give NEAR as much warnnig once it gets to its limits ]
i found this out first hand when i threw a set of TT 300ZX wheels on the back of my 1991 NA. it was WAY too easy to sldie the back end compared to my stock 205s [ which im actuly running 215 ] and it didnt let me know it was about to slide.
all in all you can look at it like this. . .
the lower, wider the tire the less warning it will give to letting go at the limit. BUT it will also let go more smoothly [ in most cases ] and come back softer.
when i go to the track this is what i run and i have NEVER spun out nor have a plowed a corner.
Front = 15mm spacer with the stock 195 / 60 / 14 @ 35psi
Rear = 25mm spacer with 215 / 60 / 14 @ 38psi
it all boils down to how you drive an what workks with your driving style.