Luke, I run 7X15 et25 with no spacers on Leda coilovers. If i went to 8X15 to fit my 225 R888's I would need to go to et12.5 to keep the same distance from the wheel edge to the shock. So going up by 1J on the width means you need to reduce the offset for the same wheel/tyre shock clearance. If you need to use spacers I try to keep to a minimum so you still get the centring effect of the centre spigot. Either that or use hubcentric but the minimum is about 14mm spacers.

Ive not tried my 888's yet but reckon they're gonna be a git to fit tbh!