Root the phone. How to do it is already here...
rm -R webviewCache
ln -s /sdcard/webviewCache webviewCache
You are changing to the cache directory.
Deleting the web cache directory.
Making a new one on the sdcard.
Linking symbolically the new one to the old one.
Now open your browser and surf. Your phone does NOT know you did this and it thinks it still has the old one. If you plug your phone into your computer and check you will see a lot of files with 8 character names. (after having surfed of course)
To your phone it is as though the webviewCache is still in the same spot. In reality it is on your SD Card where you have plenty of room for it.
After doing this to my phone a few hours I tried dowloading an app from the market and I was getting error messages. So I reset my phone thinking it would fix the problem but when i tried to get pass the google log in screen it said my account didn't have the data plan. I re-flashed using the RC28 update.zip file and got it back up. just my experience