Mikhail ZinshteynCalMattersThe campaign to expand free tuition to more low-income California students has been riding a wave of unanimous goodwill, despite its large costs. But the state’s, and nation’s, largest public university system has made public its concern that key trade-offs required for that expansion will be a financial burden for some middle-class students.Backers of the effort said those concerns are misplaced. How and whether lawmakers choose to respond will affect the fate of tens of thousands of prospective college students in California for years to come.Officials from the California State University Chancellor’s Office warned the Board of Trustees Tuesday, May 24, that while it projects a net increase of nearly 29,000 students overall who’ll receiv