I think the closer the ID of the footing is to the OD of the shaft, the greater the strength. You don't nee much room for glue. Many carbon inserts are "belled" on the front end and will actually be a larger OD than the shaft OD. Therefore, it is best to slip the footing on before you install inserts or before you fletch. Otherwise your footing will have to be larger than you want or need.
As Charlie said, the purpose of the footing is to prevent the shaft from splitting if the insert tries to push back. The tighter the fit, the better. A 2016 might work, but I think it will be too tight. A 2117 is the next closest (of the common sizes) and that size will be pretty big and require lots of glue (compared to the 2016).