Most 'bents have a longer wheelbase than upright bikes, but it is still possible to use a fork mounted bike carrier from Thule, Yakima, Saris, etc with them since they all probably make specific recumbent-capable fork mounted carrier. A quick Google search shows a Thule version:
http://www.orsracksdirect.com/thule-...rack-590r.html
That is a link to an online retailer of bike racks, however you can look at Thules or Yakimas or Saris' site for more information.
Of course, you're best to also research directly on how wide crossbars you will need if you want to figure out how many bikes you could carrier with a 'bent there since most 'bents I've seen are a bit wider than standard uprights, at least where the seat is.
Since I see you mentioned you have a hitch mount bike carrier, I would say that if you can afford the roof rack, the above link I put is a roof-mounted bike carrier. I don't know of any options to use a hitch mounted bike carriers for bents but you can always ask Thule if there is an option for that. If your 'bent isn't too wide, it might be possible, though not sure if you would be able to actually carry 4 bikes with the 'bent on it.
Jay
