The Yepp Maxi EasyFit seat does fit in the forward position on an LT2 FlightDeck, but it is tight. This is because the deck starts wider in the front and tapers to be more narrow in the back. This was a change that was necessary for the most recent model improvements. Please note the the Yepp Nexxt Maxi (found here) WILL NOT work on any Xtracycle brand bike.
When installing the Yepp Maxi EasyFit on an LT2 FlightDeck, you definitely need the Yepp Seat Adapters (found here). When mounted in the forward position, the Yepp Maxi EasyFit wheel guards (they are there for a normal bike, not a longtail) on the Yepp seat tend to "flare out" - mostly an aesthetic issue caused by the wider deck. The Yepp wheel guards are necessary for a normal bike (where children's feet getting injured by exposed rear wheels is an issue) but these guards are rather vestigial on a cargo bike, where there is already protection from the rear wheel when bags or WheelSkirts are in use.
It is possible to cut the wheel guards off or alternately, to drill a small hole in each and pull them toward the middle of the bike with a zip tie. If cutting them off, please keep in mind that this will void your warranty on that bike seat. While the flared out legs will be noticeable at first if you decide to keep the wheel guards, most riders have reported that it did not take long for them to no longer be bothered by the slight modification.
Unless you have two Yepp Maxi EasyFit seats installed, you may put the Yepp seat in the rear-most position to allow for a larger adult or child to sit further forward which improves the handling of the bike.
Note: The LT2 FlightDeck comes on LT2 EdgeRunners, Cargo Nodes, and Leaps. This article isn't applicable to LT1 FlightDecks found on some FreeRadicals, 2013 and 2014 EdgeRunners, Radishes and Cargo Joes. See what deck you have here.