Hi Keith,
In response to your two questions the first being of why we should reinforce the fuselage near the stab.
Stabs that are the plug in type ie: on joiner tubes, usually have both the spar joiner tube and the anti-rotation pins glued in position so they cannot move ( fixed incidence ). By fixing these tubes in position, a strong joint between the two insides of the fuselage is established with the result of an inherently stronger area. However, if you use stab adjusters there are a couple of types that I know of. One replaces the straight through anti-rotation pin at the rear of the stab with two independent pins, one into one stab half and one into the other, this allows you to set the incidences independently of each other. This effectively means that the rear fuselage sides are free to move in and out ( flex ) under load. The other is the type that still joins the two stabs together but moves both stab incidences at the same time, still no fixed point at the rear end though. If I were to fit this system to an airframe, I would add extra formers to this area which not only act to increase the structural strength of this area but also help to absorb the effect of loads placed on it.
As for the types available, one brand I can suggest is MK which is widely available on the web.
Iv'e seen adjuster sets in use on several models with good effect but have been told that they can eventually wear with time, I'm happy to use more traditional methods and save myself a lot of fuss![sm=spinnyeyes.gif][sm=spinnyeyes.gif]

I'm no expert, but I hope this helps!

Andy P.