To tow tandems, you'll need a commercial Class A with doubles/triples endorsement. The non commercial allows you to tow larger weights, I believe over 10,000lbs or so, can't remember the exact number.
2003 F350 6.0PSD CC 4x2 LB
Line-X, 18K Hidden Hitch, Prodigy
2003 Aljo Scout 258 by Skyline
2001 Harley Davidson 1200XLH
Wife, two kids vintage 92'& 94'
a Long Board and three Boogie Boards