Well the particulars are what they are. Constitution was indeed longer than that class of 64s. From 3 decks:


Agamemnon: Length gundeck 160'; Keel 131'. Burthen: 1383 tons. 1794 Broadside wgt 678


Constitution: Gundeck 174'; Keel 145'. Burthen: 1576 tons. 1798 Bs wgt 588 (no carronades). Later up to 800 lbs with carronades


Obviously a 2 decker would be larger in general bulk, but shorter. So the model may well be correct.