I'm starting off with 15" off an E36 205/65/R15 but I plan to get 17" made by Image to fit the car once I've used up all the tyres I have (I also have a set of 195/65/R15's with new tyres) - will also give me a little time to save up for them! As for size I was thinking 225/45/R17 same as what I have of my daily driver. Maybe a bit wider at the back to help put the power down given how light the car is. I really like deep dish alloys.
Once I've done the body work fittment I will try taking one of the wheels of my E46 to see what they look like on the Sportster. I did see on the Marlin owners club forum that some one was trying to fit M Roadster wheels, I think they are 255 at the back and 225 at the front both 17".
EDIT: Here it is (the wheels on my donor where 15 not 16 as I put the message though)
http://www.marlinownersclub.com/foru...read=611&cat=3
Dont think it really went very far.