If your intention is to do credit card touring with the ability to do the occasional night camping, it seems excessive and unreasonable to spend too much of your weight or money on camping gear. I figure that for occasional use, light weight gear is better. No sense hauling around a five pound tent that only gets used one day, especially when a one pound tarp can do the job just as well. So to, there is no need to spend a lot of money on gear that isn't going to see much use, a nice inflatable sleeping pad might be more comfortable (ok, it is more comfortable), but if you only use it after a long day in the saddle, chances are you're going to be sleeping well no matter what.

If you want to spend some more money, upgrading to an inflatable sleeping pad will save you bulk and give comfort. The new Neo-Air Xlite looks fantastic, at least on paper, I haven't seen one in person yet. A Silnylon tarp will be lighter than Tyvek and pack smaller too. You can also get silnylon in colors other than Dupont advertisement white. You can go for a tarp tent as well, and get an enclosed structure, although you loose some flexibility.

I think you really need to ask what you want to do with your tour. More time spent camping means more money spend on camping gear. If you just want to use it as a contingency plan, then I wouldn't hesitate to skimp.