When done correctly, almost nothing is a hack:
http://www.mx6.com/forums/showthread.php?t=73189 (Fun with RX7 rims)
This doesn't apply to 99% of customers you probably see in your line of business Adder. To reiterate what Magik8 said, the stock size on the 88-89's is 195/60-15 for the GT's and some LX/DX...mostly DX I believe? got 185/70-14. I can post a page from the shop manual if you'd like?