Please follow the manual's instructions. We do not know if Evenflo tested it with the infant padding forward facing and it failed....or if it was not tested that way at all...or otherwise...
Does the buckle have multiple positions? Can it be moved forward?
It may not even bother him at all.
Did you just purchase this seat for him to use forward facing? If so, can you return it? It will not last him nearly as long as so many other seats on the market, convertible OR combination seats, in the same price range.
If you want to keep him forward facing and do not have a younger child to hand the Symphony down to, I'd consider a combination seat, such as the Evenflo Secure Kid, Graco Nautilus, Britax Frontier or Pioneer, Recaro Prosport, or Harmony Defender 360.