Lovely set of wheels 
I think your wrong there with the offset. Go onto a offset calculator and thatās not what they say. It doesnāt just move like your saying as the wheel centre line is moved because the wheel is not as wide.
The way your working the offset out does keep the wheel in the same position on the inside face not the outside.
Thatās right, they are not as wide do they canāt be the same inside and outside. There inside of the rim is the same as the std Rimstocks. The point is they are not too close to the chassis and there will be more room on the outside of the arches.
Yeah so you need spacers, the standard wheels sit to far in so these must be well in the arch.
Canāt see why, I expect Lotus have a better idea where to locate the wheels than visual ālookā. If you want them to look wider visually maybe, doubt you can see half an inch. Better to keep the wheel where it should be on the inner side as it will have less of a turning moment. However, doubt that has any effect, biggest concern must be avoiding and risk of rubbing.
They came off a race car used with no issue, they fit my car with no issue, they line up where lotus intended the wheels to sit and donāt need spacers to get the correct positioning. If you want wider wheels thatās a different matter, I would agree, donāt fit spacers to make wheels look wider, buy wider wheels.
Mind you, take a look at the Motorsport Elise which has the same size wheels, looks like the same tooling. The wheels look pretty tidy.
Bored with this now.