Originally posted by warbirdz1
Gentlemen.....Most of the modern era aircraft(Jets and the Like)...have had the advantage of excellent windtunnels and CAD programs for determinig aerodynamic feasability of designs and practicality of buiding them.....alot has changed in a short period of time......F-16, F117 ,FA-18 along with Boeing 777 and A-319,320,321 330,340 are just a few that use computers to do the work that was done by pilots just a few years ago....they use "Stability Augmentation" thru computers to fine "tune" aircraft flying envelopes...so smaller tail surfaces and different designed tails are used because much is handled by computers...theres inherent instability but its offset by those computers.....Dihedral is used for stability and each plane has its own unique characteristics...I.E.B-25 has roughly 5* dihedral to eng. nacelles and 1* O/B to wing tip....with stab having 0*.A-26 on other hand has 4*-5* dihedral on wing and roughly 6* on the stab.........As you mention B-727 its horiz stab is actually slightly neg by 1/2* or so.....so its sometimes trial/error til a good combo between wing and tail is found........thats whats nice about models..If an idea doesn't "Fly"......try a different one til it does......Bill..... 
To add to this, most airliners that use dihedral in their H-Stab also use a high degree of sweep-back, which decreases stability. The dihedral helps correct this. For instance, the DC-10 uses 6* wing dihedral and 10* of stabilizer dihedral, while both have a 35* sweep back.