[Billfred]

Since South Carolina has played its only official event of 2016 featuring all but three teams (281, 1293, and 1319 are playing elsewhere), I'm defining four years as 2013-2016.

1) 4451, undisputed. Palmetto, Orlando, and Newton RAS in 2013, went back-to-back winning Palmetto in 2015 and 2016 (only three teams have), Palmetto EI in 2016, Palmetto WFFA in 2014, SCRIW in 2015, Orlando finalist in 2013 and 2015, and that's just the tip of the iceberg about those guys.
2) 343. They had a dry spell after a heap of silver from 2010-2012, but in 2014 they started being contenders again, winning SCRIW and parlaying that into winning the final Peachtree Regional and getting silver again in their subdivision at Championship. They just got silver again at Palmetto yesterday, and they should be a threat in Huntsville.
3) 1319. Won Georgia Southern Classic last year, six UL Industrial Safety awards in three years (they haven't played yet this year), and several other judged awards.

I'd say there are three teams that have a legitimate claim to the last two spots, but which two depends on the lens through which you view them:
* 3490. Two-time SCRIW champions (2013 and 2014), Palmetto 2014 finalists, regularly in the conversation.
* 4073. Palmetto 2015 winner, 2016 quarterfinalist, two technical awards.
* 4901. Orlando 2014 winner (probably a higher-quality win than 4073's, given the game and the bracket), Palmetto 2016 Dean's List Finalist.