going for 16' ?

sound proofing.
last forever.
then only change tyre.

By the time I finish with this car's installment, it will be time to change to D segment. An Audi is a target for now. By the time you get Audi still want to mod this and that meh? Already unker by that time.

I'm in the same situation, but I'm already using 16" dunno how to deal with the spare

U can look for crz and civic stock rim if u don't mind the badge

Bumpy you mean as in hard suspension bumpy or floating up and down when cruising? If it is the later, try putting in the spring cushion buffer.

blame it all on the malaysian road

cushion buffer?
adjustable?

Sorry for being unclear. For 'suspension bumpy', you will be able to feel that your car is vibrating when you go through small pot holes, making you feel that you know where are the stones and uneven-ness. This is what happen when the suspension system is too hard and not able to absorb vibration. 

However, from what I read, your case is rear suspension too soft. It goes up and down too much when you go though wave-ey roads and if you go thorugh bumps too fast. At the end of the bumps, the rear goes up and down, do not want to settle down.

first u can try add spring buffer, if still not satisfied, change to BLM spring

I did complain in posts before that the rear suspension is too oft for my liking. It waved up and down when I go through a certain portion of Kesas. Especially when I put my parents and bro at the back. It is so hard to drive at that section when the rear just do not want to settle down and let me cruise properly.

I then added the spring buffer cushion. This is not the permanant solution, but it is definitely cheaper. The result might vary towards individual, but I am satisfied with what RM160 (2 pairs) does for me. At that section, no more bouncy. Yes, bouncy is the word.

The cushion is just a rubber ring like to be put in between your spring coils. If you go to shops, they will measure your spring height and diameter when they complete jack up your car. Front Spring is larger than rear for our car.

Just to add, maybe you will want to know. I am using stock rim and tyre. Whenever I go through the same spots and holes (before and after this cushion installation), the sound is more like glung glung instead of glong glong. If you know what I mean.

I use it every time I drive. Since Nov 2012. No problem so far. I usually use the gearstick when up/downshifting at tight corners. Steering wheel pusing more than half circle, hands crossed ady. Last time jadi like that, all also I langgar. Wiper, signal.. Haha