With fund-raising efforts coming up short, selectmen have to decide whether to seek a Proposition 2½ override of more than $6 million for library renovations. In a presentation Tuesday night, library advocates said they had raised $500,000, plus $100,000 in pledges. The $12 million project has won a $5 million state grant, but it’s predicated on the town raising the remainder. Town officials initially said they would be willing to put $2 million toward the project but now will be asked to provide more. “The whole dilemma — if you don’t do it, you miss out on the state’s $5 million grant,” said Selectman Tony Vegnani. “But the town has to spend $7 million to get the $5 million.” The deadline for raising the funds is Dec. 31, library supporters said, and selectmen would have to request an override by September to put it on Special Town Meeting warrant this fall. “The dilemma for us is there will be an override for the middle school, for a new town hall, people are coming in about sea walls, senior center, there are so many issues right now,” Vegnani said.