Tim is not too big for Vera. Vera is amazingly strong for his size, give credit to that to his wrestling background if you want. Vera is accurate and deadly with his strikes. Just look at his kicks to the sides of Mir, those things punish and he doesn't land just 1. Vera has wicked long legs and isn't afraid to use them.
Tim on the otherhand has very heavy hands, but they are not that accurate and usually he jabs his opponent away and then goes for the bomb. That won't work against Vera because Vera's legs are almost as long as Tim's arms, so Tim will not have a safe zone. A lot of people like to use the Monson fight as proof that Sylvia has a ground game, it doesn't. What it proves is that 5'10 vs 6'8 even matters on the ground. If Monson had been 4-5 inches taller he would have GnP'ed Syliva till he got KO'ed or tap, but every time he postured up Tim would streth out and the distance was just too much. Monson had to try to go for subs and it was next to impossible to keep Sylvia from using his momentum due to the sheer size difference.
Sylvia does not have any decent ground game. If it goes to the ground then Vera will make Sylvia look silly. If the fight stays standing then we have a very interesting fight between a knock out artist, and a knock out artist with style. I give Sylvia the heavier hands and he could win this match with a single punch, but I give it to Vera as I think he can handle Sylvia's reach and if Sylvia gets desperate and takes it to the ground then he will be in serious trouble.