wheel offset question

[The Ghoul]

This is actully a question about my daily driver, but wheels are wheels right?
here is the situation.
I bought a set of 3 rims off ebay that I liked.
they are +35mm offset
I found a forth rim same style, dia, tread depth, and lug pattern
It is a +42mm offset
I did some lookiing into it and found that the ideal offset for my 2000 impreza 2.5RS with 7" wide tread is from +50mm to +55mm

Here is what I know about offset;
Offset is measured by the center of the tread with (3.5" in my case) to the mounting surface of the rim.
If you have the wrong offset in the - direction the weels my rub on the inside of the fender.
If you have the wrong offset in the + direction the weels my rub on the Mc pherson strut or inner wheel well
If you have the wrong offset in eather direction you will but more of a load on the wheel barrings, the savarity of wich is determaned by how much off you are, how hard you drive ect.. this may lead to shortaned barring life.

here is what i need help on, please tell me if it makes sence;
It is most efficiant when producing a product to make one mold for multipul parts that have the same genral shape but diffrent refined dimensions. They pour lots of molds send half of them to become +35mm offset and the other half to become +42mm offsets.

Here is where the first verriable comes into play, would they drill the lug holes with the counter sinks before they split the rims off into the two diffrent groups? or do they drill them after they split them appart?

after they splitt them off into groups they mill down the mounting surface of the rims to what ever desired offset depth.

here Is where my situation comes in;
If they drill the counter sinc for the lug holes before they mill the mounting surface to a unaform depth for all rims regardless of offset that would lead me to think that there is enough metal to mill off at the very least the 7mm it would take to make all 4 matching +42mm offset.

here is the second part of this mess;
reguardless of how they drill the holes in the rims; if there is enough metal between the counter sink and mounting surface to mill the +35mm offset rims to mill them down to the ideal +52mm offset then there should be enough to do the same to the +42mm offset. Seeing how they wouldent drill the lug holes for the rim with the greater positive offset deeper than they would the one with the smaller offset?

does any of this make sence to any one else?
basically what im wondering is if they would go thru all the trouble of making 2 diffrent molds for the diffrent offset sizes that are only 7mm diffrent?
Would they really change the arch of the spokes to componsate for only 7mm?
also would they drill the lug holes  so that the distance from the bottem of the countersink to the mounting surface be the same for all offsets?

man I hate being paranoid 
Im going to have an ulser or a brain embilsem by the time im 30

[phat69charger]

Check these out because I'm better with inches and the simple stuff 12" rim 4.5" BS = EASY

http://www.rsracing.com/tech-wheel.html
http://www.1010tires.com/WheelOffsetCalculator.asp

[The Ghoul]

that calaper calculator is great. thank you
I just wish I had more insite on how the rims were made....
ahh it can prolly wate untill I get the ebay ones in the mail.... I wonder how much metal is enough for alloy rims, so the lug nuts wont pull thru?.
ok now im just thinking out loud.

[phat69charger]

Your Welcome, Cudaeh   

[The Ghoul]

well I have my answer. 
turns out they drill the holes after they machine the mounting surface so there is only 20mm between them to start with. I dont think wheels will stay on with 3mm of aluminum between the lugs and rotors