Question on wheel biasing (different size F/R) and eliminating bump steer?

So I am currently shopping for new wheels and tires for my mk2 and wondering if it is necessary to have the wider wheels in back that most people run. I am looking at possibly doing 16"x7" all around, and putting maybe 215 or 225 x 40's on all 4 corners. Having all the same rim and tire size would allow me to rotate tires, save money, weight (compared to 17x8's), etc.. and the only thing I can think of being a problem is needed about a ~10mm spacer to make up for the results I get using the Mr2 wheel and tire calculator: http://91mr2.com/wheel-and-tire-calculator/

"Front flushness: 20.35mm tucked in from flush

Suspension proximity: 10.35mm from possibly touching the suspension

Rear flushness: 33.05mm tucked in from flush

Front comparison: 14.7mm farther out than the old wheel

Rear comparison: 2mm farther out than the old wheel

Rear speed change: The new tire is at 97.47 KPH when spinning at the old tire's 100 KPH"

Currently I have 16x7,205x50 Front and 16x8, 225x50 Rear.... The car tends to have a fairly large amount of bump steer and a moderate amount of non-problematic understeer. I have only experienced the snap oversteer once while showing off to a friend taking a relatively small and sharp 90 deg corner at about 50 in second gear. Most of the time I find that I can get the car to break free when I want it to and stay under control when I want it to... The only problem is bump steer breaking my wrists on potholes or any moderate bump in the road, otherwise the car drives straight as an arrow and is a very pleasant ride!

Suggestions??