My wife and have toured together for many years in small sports cars / roadsters we have come up with a very workable system. We share a carry-on sized suitcase and a quality carry-on duffel. Anything that needs to be folded and/or protected goes in the suitcase, e.g. dress shirts, dresses, blouses, make-up (hers, not mine) go in the hard side suitcase. Jeans, undies, socks, etc. go in the duffle. The trick is to spend a little money on a quality duffle.
Here's my current favorite:
Oil Cloth Weekender Travel Bag - Duluth Trading
I, alone, can travel for over a week with that duffle with no problem. I also tour with a DSLR camera in a backpack style camera bag and it all fits perfectly. A 370Z roadster has lots of room with a little planning.
Don