here's a list I have compiled from the info on rx8club.com of offsets used by jap tuners.
key:
company name; front wheel width (inch); offset (mm); distance out from std(mm); rear wheel width (inch); offset (mm); distance out from std (mm).

revolution---------9.5---------38---------31---------9.5---------42---------27
fujita---------------9.5---------35---------34---------9.5---------35---------34
knight sports-----9.5---------35---------34---------9.5---------35---------34
ings-----------------8.5---------22---------34---------9.5---------34---------35
mint blue-----------8.5---------40---------16---------9.5---------45---------24
odula----------------8.5---------32---------24---------8.5---------32---------24
mazspeed Ms 01--8.0---------40---------10---------8.0---------40---------10

I reckon the revolution offsets are mixed up (front and rear) but that's how the info was found.

here is some info that members have published. (if your listed and want to be removed or I have it wrong PM me)

cortc axis hiros 19"--8.5-------45---------11.35---------9.5---------55---------14.05
myrx8yourcar ssr --8.5---------45---------11.35---------8.5---------45---------11.35
davefrz 18" weds--8---------42---------8---------8---------42---------8
kel rx8 20"----------9---------38---------24.7---------10---------44---------31.4
feed spacers -- 8-------------32---------18---------8---------27---------23(offset with spacers)
danalo work misters 18”--08---------51----------1---------9---------63----------0.3
recommended---------8.5---------45---------11.35---------9.5---------43---------26.05

note these distances are only calculated ie the rim and tyre can be futher out.
kel Rx8 has the widest offset change that has been posted by a forum member. it rubed but the guard lips were modified to stop it. so any increase around this is likely to rub.