Unfortunately you can't resize the split. I almost never want an exact 50-50 split. One webpage always scales better then the other in split mode.

You guys need to rotate your screen 90 degrees.

Don't know about you, but on the latest release (1.6) I can resize the split to be between 10-60%

You could have one site set as a panel and resize.

Thanks. That is what we are all about. We believe we all deserve to get a browser that can be made to work just right. Thus we have the motto : when in doubt, make it an option.