Just the two of you, or do you have kids? I would guess your pin weight will go up 300 -500 lbs once you actually get a "real optioned" trailer. Case in point, my trailer showed an unloaded weight of 7869. Actual delivered weight was ~9200 lbs. Actual weight loaded and rolling is ~9800 lbs. So I would suggest going to a dealer lot and checking out what an actual trailer weighs and then just figure the percentages to get a guesstimate of the pin weight.
FWIW, I towed our current Fiver with a F150 that had 2400 lbs of payload (HD payload package, crew cab 2wd), and we were within 200 lbs of exceeding the payload capacity with our family of four (~450lbs of people) and our stuff. Part of payload was taken up by the 200lb superglide hitch I use. A standard fifth wheel slider will be more like 100lbs, plus ~50lbs for the rails and install hardware.
Current TV:'14 F350 Lariat CrewCab, 4x4 Short Bed SRW Diesel w/ Pullrite 2700 (16K)
Current Fiver: '15 Puma 295BHSS Anniversary Edition
Past TV: '13 F150 HD Payload SCrew EB, '08 Tundra CrewMax 5.7L, '02 'Burb 5.3L, '97 Dakota 3.9L
Past Trailers: '09 Wildwood LE 27RB, '02 Palomino Yearling RL, '87 Jayco 1006dlx