What's the recommended spacer size for 4.4 with style 87 wheels staggered setup?

[X5only]

What's the recommended spacer size for 4.4 with style 87 wheels staggered setup and without fender flares running 20's tires 275/40 front and 315/35 rear? I'm not sure what maximum spacer size to get that won't result in rocks being thrown up the fenders. I've searched on this forum, but the recommendation is for 4.4/4.8 with fender flares - 15mm front and 20mm spacers running 20's 275/40 front and 315/35.

And the consensus is H&R DRA spacers. Now I just need to know the max size spacers to get for the front and the rear.