Re-doing the math...
Doing the math:
Fronts:
8" wheel with a total width of 9" = 228mm
half of 228 = 114mm
40mm offset means
74mm to outside of wheel
154mm to inside of wheel
measured distance from hubface to outside of fender = 64mm
measured distance from hubface to suspension = 170mm
So our 40mm offset 8" wheel should extend 10mm beyond the outside of fender and have 16mm of clearance on inside.
Rears:
9.5" wheel or 10.5 total width = 266mm
half of 266 = 133mm
if we switch from a 20 to 40 offset...
93mm to outside of wheel
173mm to inside of wheel
measured distance from hubface to outside of fender = 90mm
measured distance from hubface to trailing arm = 170mm
leaving 3mm jutting out beyond the fender and smashing into the trailing arm 3mm