Tire sizes?

[Bean]

I assume you are aware that the difference between a 195/50R15 on a 15x7 and a 185/60R14 on a 14x6 is 500g max per wheel&tire combo. Also with the above example that keeps your speedo about the same you wont lower the car in any way and therefore neither the car weight center... If your serious about saving unsprung weight then you need to drop some big cash on a set of TE37V (usually about 1-2kg less than the competition) and a custom brake setup... I personally have an AP big brake upgrade in the plans that should lower the unsprung weight by around 3kg per corner.
To make another example a set of alloy wheel hubs will save 1kg per side, if you want to go further the modception bigbrake kit will shed 2kg per side. These difference are disregarding the wheels themselves.